You're not supposed to hate her, you're supposed to laugh at her for being so self-deluded. And yes, she is selfish but she gets her comeuppance at the end when she finally gets what she always wanted (to be famous) but at the expense of everyone in her life leaving her.
I seriously don't get how Miranda Sings is funny? She's making fun of people with intellectual disabilities. I think if she did that character in a room with hundreds of mom's with disabled children, children with syndromes, autism, Asperger's, mentally delayed/challenged, etc. they would not find it at all funny. Shame on Colleen Ballinger.
The thing is a lot of people think that disable people are little angels but lets be real here. Not everyone is an angel.
It's kinda like how they tend to exaggerate the "good" quality of a person after they die ignoring the bad ones. When we know it aint the truth because no one is perfect.
I like the show for the fact that it tries to be different and real.
She's not making fun of anyone with a disability... when she originally created the Miranda character, she was actually making fun of people on YouTube who all thought they were amazing singers.