I'm interested in a girl in my circle of friends. We know each other as friends, but I decided to try a bit harder to see how far I can go.
The first thing I did was talked with her the whole night at a party.
The next day she asked me whether I would help her with maths. Of course, I said yes, and asked how we should proceed. She said that I should drive to her house when I turn 18 (which I did 2 weeks ago). I took this as a big hint - although one of my friends warned me that maybe she isn't meaning it that way.
I didn't think much of it, but when I did something with my friends (cruising with my car and going out to eat) she always said something like: "You went there without ME". For me that's a hint, so the next logical thing would be to ask her out, so I did.
I asked her whether she wants to go to a burger restaurant with me, she said yes. So far so good. The thing is the day when we wanted to go out, she said that she has a bad headache and asked me whether we could tomorrow. If she doesn't want to go out, she could simply say that to me. I repeatedly asked her whether she was ok with my plans and she said it's all good and I'm not putting pressure on her.
The real problem started the next day (the backup day). I texted her saying that I would pick her up in about 3h (so I would be sure that she has time for me) - right off she responded: "I can't go out :(".
I didn't message her since that moment (we are sending pictures on Snapchat, but that doesn't mean anything). I don't know what I did wrong, so I wanted to talk with her about that whole situation (which I didn't do yet).
I just don't understand why she keeps complaining that I went somewhere without her and when I propose something she firstly accepts but then stands me up in the last minute. I don't want to start a conflict, I want to solve it.
How can I talk to her about this while avoiding to start a conflict?
Edit: I know that she has hard time at the moment, because her father died some months ago. She tried to call some time ago to talk about that, but I was sleeping and so missed her call.