The Patrick conundrum
This film would have been better off without Patrick. Patrick made both Will and Lou look like much worse people. There's no acknowledgement of this in the film, but the rational viewer is forced to this conclusion anyway.
The first important thing to acknowledge is that hypergamy is the natural female state. Evolutionarily speaking, it has a lot of advantages. Practically speaking, it lands women in a lot of bad relationships and is the bane of average looking but good hearted/reliable men everywhere. But it is what it is.
They were careful in casting an average looking guy for the role of Patrick. If there were any ever films where the female lead leaves a more attractive guy for a less attractive one, the boards are full of female outrage. There are even posts on this forum that say Will should have lived simply because he was handsome.
Let's analyse and then sum up.
The relationship.
Their relationship is very non-intimate, acquaintance like for people who have supposedly been together for 7 years. Perhaps it's because he's complacent and she's flighty, but generally people who have been together for 7 years have much stronger emotional ties than depicted in the film - where the relationship ends on a simple walk out. It's also odd that someone who is Christian from a Christian family has not insisted on marriage yet. This is obviously for plot convenience as it's a little easier if there's no marriage breakup involved. We are seeing a trend of films though where women unapologetically end long term relationships after meeting someone new (I saw Take This Waltz recently too which is similar).
Patrick's choices.
In one way, the writer is brave to not go too far in justifying her infidelity by making him turn total creep. Normally the convenient thing is to have him cheating and her find out, but this would have rang false for the character - who seems fairly devoted to Lou even though preoccupied with his fitness pursuits. So instead they made him distracted and selfish seeming - although it was pretty ham fisted. There's nothing inherently wrong around planning a holiday around some event one partner or both want to attend. However, this also makes it more troubling in a way - the message being that if you're not constantly working to keep your girlfriend or wife deliriously happy, she has justification to cheat (by pursing other relationships) at any time.
Ultimately at least they have him walk out after realising she's no longer in love with him. But this is convenient for her too, as it let's Lou completely off the hook without having to seem too much like the villain - waiting for him to figure out she's fallen out of love rather than doing the brave and assertive thing and breaking it off herself. Anyone who watches the scene and thinks it's unreasonable for him to have problems with Lou taking Will on a romantic resort holiday, even under the circumstances, and to not know full well that it will further progress the feelings he knows his girlfriend has for another man is kidding themselves.
Patrick actually comes off looking pretty good, although he is the film's biggest loser. There's no happy ending for him.
Will's choices.
Good looking men, especially those who also have wealth, know they have power over women. That's ultimately why so many of them are creeps - power corrupts. Not only do they tend to cheat, they tend to entice a lot of women to cheat, to "play the Hottery". It's a game.
It was wrong of Will to entertain romantic feelings with Lou. He later states in the film he didn't want to because he wasn't able to give her the life she deserved, but hang on - what about because she's already in a long term relationship? No qualms about that, William?
That's because parts of "old Will" are still there. He sees it as challenge, to see if he's still "got it", the ability to charm a woman out of her existing relationship. And he succeeds with very little effort - even knowing it will last at most a few months. He even taunts Patrick after meeting him, knowing that despite being in a wheelchair, has effectively emasculated him.
Will is a predatory creep. The fact his previous gold digging girlfriend left him when he became paralysed doesn't give him moral justification to seduce someone else's girlfriend and break up their relationship too.
Of course he dies at the end, so it's not exactly like he is rewarded long term, although he gets to make his last few months a lot more enjoyable.
Lou's choices.
It's clear early on that Lou is infatuated by Will's looks and wealth. Part of her determination to "crack his shell" is her disbelief someone so handsome could be so dour. Lou allows herself to fall in love with Will. True, she has to spend time around him as that's what she's employed to do - but the level of intimacy she chooses prior to the breakup with Patrick is already infidelity. Before people cheat physically, they cheat mentally and emotionally. This is why she is dishonest by omission with Patrick about her "job".
She has no regard for Patrick's feelings, her boyfriend supposedly of 7 years, consumed instead by this interesting new man. Feeling perhaps he's losing her, he buys her a necklace with his name on it - but she is completely underwhelmed and shows it. She then ostentatiously squeals with delight in front of him at the gift of another man. Are we really meant to believe she does not understand how this is going to make him feel?
She then lets him walk rather than doing the decent thing and ending it after she has clearly fallen in love with Will. Almost like she was keeping her boyfriend of 7 years a backup just in case.
Lou comes off looking pretty bad, but has the happiest ending - with a big cash payoff so she can travel the world.
Now, I understand this is a film written by a woman for a female audience. A lot of women view being "trapped" in a boring (ie. stable) relationship with an average looking but perfectly nice man as a fate worse than death - at least until their youthful good looks are gone. Women make these calculations when they view this kind of film based on what they would want for themselves and most would view a fling with a handsome guy, wheelchair or no, plus a cash windfall at the end of it and thus the freedom to pursue handsome but unreliable men as more than a worthwhile trade.
But objectively, Will and Lou are ultimately selfish people and Patrick's feelings and life are a case of "if you're not good looking, your feelings aren't important". Remember, he also invested 7 years of his life in that relationship. That's 7 years he could have spent doing other things or finding a woman who would actually stick around and not leave him for the first handsome man to distract her with his dimples and trust fund.
Obviously there are mitigating factors in this love triangle. I don't personally believe people should remain in loveless relationships, even if they aren't abusive, but such relationships usually become that way because one or both people have given up trying - and this can happen rapidly. If you open yourself up to new feelings with new people, you can't help but weaken your existing relationship. It doesn't mean there was something wrong with it to begin with. The brain chemistry is different. New relationships are kind of like a drug - they release many of the same substances in the brain. And like a drug, you can get to the point where each "fix" lasts for a shorter and shorter time before you need a new one.
Let me know what you think. It's just interesting to me to see how the writer and filmmakers treat the character of Patrick and how easily dismissed are his feelings.