It is disappointing, while I agree she might have genuinely had something important come up at the time you were meant to have the date, she could equally be a flaky person and got cold feet. It’s up to you if you want to give her another chance, or benefit of the doubt, but I will say it’s better to just nip it in the bud if she comes back to you, then doesn’t apologise *and* make up for it properly, or doesn’t have a real (or a vague) reason for not answering the phone. If someone really is interested in you, their behaviour would likely generate less of these nagging doubts and second guessing.
I’ve had ‘friends’ in the past who have done similar (the worst example in my case saw me waiting at a bus stop for over an hour, for someone who wasn’t even coming; they’d changed their mind overnight and didn’t have the courtesy to text me! We’d been friends for a few years but not for much longer after that, especially as it wasn’t the first time she’d bailed out on me. I just didn’t see the point any more, and I felt better when I stopped talking to her, because the perceived rejection really was eating away at my self esteem).