Why did she marry him?
I don't really have a problem with the age-gap between the two leads but it never felt like the woman loved Tim in a romantic sense. That was seemingly the point of the film. Others thought she was this older woman taking advantage of a vulnerable younger man but that was their narrow-mindedness rather than the truth. There can be a close, yet ultimately platonic bond between men and women, across the generations.
However after comforting Tim for the umpteenth time after the death of his mum, she then falls head over heels for him? I don't see the motivation for this change of heart. Tim hadn't changed as a person. Marrying someone isn't a conventional way to cheer someone up. What prompted the shift from her being a maternal figure to passionate sexual partner? Can I expect to get laid thanks to a family friend when my dad is visited by the Grim Reaper?
I was hoping they wouldn't get together in the end as the idea of them having rampant sex is disturbing considering beforehand she was doing all the things a mother would do for a child bar breastfeeding and wiping his ass. It sort of feels like she groomed him, particularly with her being the one instigating the trips to the beachhut.