((hugs)).
I've been there. I've debated whether to remain friends with someone who would flake or not be there in the same way that I am there for them. After reflecting, I have grown to accept for whatever reason, some people are just unable to be that person that I want them to be.

Some things to think about:
1. It is nothing to do with you! The person definitely has their own issues, although there's no need to accept this kind of behavior from them, since it is clearly hurting you. 2. Take care of your own needs, and know that you cannot rely on this person, although you can still maintain a friendship if you choose (maybe just not the kind that you want) 3. You can keep your distance more, and you always have the option of talking to them about it. They won't automatically change their ways, but sometimes this person might be more mindful and respectful of your time by knowing it bothers you.... or ....4. You have the right to walk away from this friendship, if you choose. Some friendships aren't meant to last. It's up to you whether this is a deal breaker, and it's acceptable either way. Don't compromise your values, health, or wellbeing, if this friendship is destructive.

Although we cannot change others, we can change our response to them, with time and acceptance. I know it's sad not to have expectations since some people fail to live up to their word, but the more you shift your focus on to other things, the easier it will become. I also hope with time, you'll meet friends you can rely on more, maybe joining something or over a common interest, if you choose.