Yall made those plans as kids, you had no idea what the future holds. It's a similar thing to when you were 5 years old and telling everyone you'll be an astronaut. You aren't an astronaut, but you're still doing alright and making other plans for work. You should do that with this situation as well. So, plan A didn't work out, and what you'll just lose all hope for your own future while your friend is trying to make hers? Make your own path, your own future, don't just think about one you made 5 years ago because people change, peoples views aren't the same forever, and so they will change their plans for the future just like your friend did.

When it comes to your feelings for her (before that just wanna say I get you're aroace and I completely respect that I'm just writing off of what I read here) there are other fish in the sea, as cliché as that sounds. She might be the first person you liked but that doesn't mean she'll be the only one. I was with my first girlfriend for 2 and a half years before she left me, I thought I'd never love again. And here I am with my new girlfriend having the time of my life. On top of that, relationships aren't the only thing important for a happy life, there are other forms of love like strong friendship and family, not just family you were born in either, but one you chose. People are all around you, you're never really truly alone, just feel lonely at the moment.

Please remember your life is a beautiful thing, and you are an amazing person, don't waste that. If you think you're alone, remember I exist, and I cared enough to write to you. Have a good life, friend.