They always cancel on me

So my friend/mentor who’s 10 years older than me 9/10 times cancels on me. But today she went too far. A couple days ago we were gonna meet but she canceled cause she was “too tired” but I got no sleep last night and i was still gonna meet today. So today we were gonna meet but she said “her hair was wet” so we had to wait a few hours after her meeting. I followed up with her a few hours later and she said she had to cancel cause she had to go to her parents house and then have a date night. Sometimes she’ll cancel and then I’ll see a post on Instagram of her hanging out with her friends. She just always seems to have better people to hang out with than little old me. She’s really the only close friend i have and i feel like i have no one else to talk to but I feel more loyal to the friendship than she is. I felt so unimportant to her after all this today that i relapsed into self harm. I don’t know what to do. I have a good time when I actually hang out with her, but she doesn’t seem like she takes the friendship seriously.