What are your thoughts on me telling a girl I liked her when I knew she had a boyfriend?
Why are you telling her you liked her in that time frame?
I'm crushing against her for half of my life
Telling someone that you like them while they're already in a relationship is being inconsiderate to them. You know they cannot respond to you even if they wanted to so in the end you burden them with emotional baggage.
But that's not my problem. I'm too good for her anyway.
It's best to keep your feelings to yourself when you know someone is unavailable. And if you think you are too good for someone, it's best to not even consider wasting their time.