Wow, thank you for sharing all of that. It must have taken a lot of courage! You see yourself soooo darkly. It's true what they say, that we have no greater critic than ourselves. I'm an older man, so you may not take my words, but the emphasis on looks has nothing to do with your generation. It's largely about your age, unfortunately. High school especially is just a cesspool of bitter shallowness. Teenagers usually don't know how to value emotions or personalities yet because those are such complex things to evaluate. College age is where people really start to value things other than looks, because looks are such a temporary and fleeting thing.
And what's worse, you're comparing yourself to someone who's 29, so of course she more well-developed and intelligent, she's had more than a decade of experience to grow from. 17 isn't the prime of our lives, we're still just developing then. Be patient with yourself and take this time to learn and grow.
On top of all this, I feel it may be important to find a therapist. Self-esteem this low has likely been caused by something that can be resolved. You need support an caring from people around you. You'll get that here from us of course, but you need people in your life you can count on as well. A therapist can help you build that vital support system.
I fear these words mean little when you feel this way, and I can easily understand as I felt so similar when I was your age. And I'm not saying that it's just a phase or just your age. I'm just saying that it's not fair to yourself to compare yourself to someone who is so much father in their life's journey.
Please share more,k and I'll offer whatever support I can. I feel for you.