we agreed to go to the beach on the third date. 15 minutes before the date she messaged and cancells the beach date and offers to meet 3 hours later and go to the cinema. the reason for flaking was her studies. I felt that she was reluctant at first to go to the beach at first but then she agreed then she flaked 15 minutes before the date. i know that studies is not the reason. why is that and how should I act because I hate flaking the last minute?
If you hated don't ask her out again. Guys are really strange human beings. If I don't like something a guy does and I'm not in a relationship with him, I cut ties. You want to see this girl again for real or do you just want to have sex with a or tried to have sex with. Get your own head together. There are other reasons besides studying that are legitimate and that is the break that I would give to her. Maybe she needed to take her little sister to the hospital for open-heart surgery – something serious like that. Perhaps she had diarrhea and felt like crap. If you want to give the girl a break you have a multitude of possibilities and potentials to consider if you don't, then cut
If she's blowing you off, yeah you should tell her that it's bothering you. Also, you have a complete right to ignore her messages, not contact her, or cancel plans because she did the same. She clearly doesn't care about your feelings or your wasted time, so you shouldn't either.
I personally don't think she was doing it to flake. Some woman (or people in general) are uncomfortable being out in public half-naked, because they are in a swimsuit. If you two planned on not wearing your bathing suits, then it could be a different story, but she may be uncomfortable revealing her body to you, or to the public, or both. You said that she was reluctant before she agreed on the beach date. I think that's her message to you saying "I'm not comfortable with that". Also the fact that she wanted to still go out, to somewhere different, is probably saying that she just wasn't fond of the beach date idea. Don't draw the flaking conclusion too early.
Because she was nervous about how she would look. You didn't think twice about it, but you are pretty much naked at the beach. Lots of people don't feel comfortable with this. So she flaked because she was afraid of you seeing her half naked.