Something similar happened to my partner and I. I was madly in lust for her, she wasn't ready so we decided to remain friends. I got a boyfriend, and she tried to kiss me while I was dating this guy. I let it happen a little bit (the kissing) and I felt guilty, so I dumped the guy I was dating thinking she would date me if I was single. Nope. She ghosted me. So, I started dating another guy. Same thing happened, she kissed me and I dumped the guy. This time, however, I was not ghosted. Instead, I remained single and she and I stayed close friends. Then she introduced me to her parents and I started spending the night with her, often. After two years of wanting her, we went on vacation and she told me she loved me. We've been together ever since. Love is weird, and there's no predicting the future. Do what feels right. If she's as in love with you as I was for my partner, none of her relationships will work out. Stay in her life, be supportive, and remain friends.

Also, being flaky really hurts the other person. I was in agony for two years before she finally came around.