Ok here is the deal. One month ago I number closed a girl from my course. We have very good chemistry and everything is fluent with her. However after n. closing her I asked her out for drinks with the result of her answering:

Me: hey how are you! Wanna go for drinks on Saturday?

Her: I'll have to see. I'm in the Library at the moment and Idon't know for sure. But I'll let you know

She didn't propose anything so the next week I asked her again and she replied with a very similar answer (saying she would tell me when she has time).

I thought everything was finished and I moved. However yesterday, after two weeks of not texting her I receive this message:

Her: Merry Christmas "my name". Still looking forward to actually getting to meet up with you! Though so far its been my fault that we havent . Hope you have a really nice holiday though .

I think either she is into me completelly so that to think about me even two weeks after not talking or she is just playing around and looking for guys to increase her selfsteem.

who knows exactly , you might know that or can work it out , she could be shy ?

but this is the message i would be replying with

Hey , i am having a fantastic holiday , yes you are right its your fault and you have 1 last chance so meet me at x at 7pm on sat night and dont be late as you will be buying the first round

Correct response: It's cool we'll do something when you know you're definitely free, let me know what your schedule is like.
that is a fine thing that she texted, it sounds like she's interested in meeting up
when she texts that means she is reaching out to you, - set a specific date, don't pussyfoot with too many messages - meet up, have fun, and see where it goes

who cares about the second paragraph about why she is interested at this early stage? how can you possibly know? you don't have enough information yet, any conclusions you reach are just stories you ahve told yourself, that sound like you are trying to talk yourself out of risking your ego

after a date you can decide if you want to pursue further or not, if nothing else you will get some experience creating chemistry on a first date

_________________
those who say it can't be done should get the fuck out the way of those doing it

It's crystal clear, you did not show any dominance. You asked for her validation to go out for drinks. Instead, try saying something like "Hey, when are you free?". When she replies with a date, tell her to join you at place X for drinks. Notice that I did not say ask her, I said "Tell her".

Example: "Join me for drinks on Thursday at 8:00 pm".

This is just an example, but I hope you get the point.
If there's something you can surprise her with, it would be even better. I always use the line "I have a surprise for you", and she keeps wondering what it is so she comes and we end up at her/my place. That's basically the surprise and I'd tell her about it when we're done.

Guys thnks for your help I didn't know I was going to get this many answers haha. Thnks to you I now understand that its not such an issue. I'll follow your steps. However I forgot saying that we are both on holidays and I wont be able to see her for two weeks or more (After Christmas). How do I maintain her interest?

You don't really maintain her interest for 2 weeks. Just wish her a merry christmas and a happy new year and game other girls meanwhile until the time comes.

I detect some disinterest from her. If a women is really interested she usually will suggest an alternative date/time for meeting up. 'Ow, I'll let you know' is girl language for I'm not really into you but I'm being polite.
Women don't like confrontation. So it's easier to give an indirect rejection.

My advise is to move on to the next women. Don't waste your time with flaky/disinterested women. I met a booty-call on new years. I F-closed her a 3 years ago. Got needy and she never responded to me again. She opened me that night and asked me for my phone #. I wouldn't have asked her since I knew it wouldn't go anywhere. But since she took the initiative I went with it with zero expectation. We both agreed to maybe contact each other. Smirking at each other.

2 Days later I messaged her and she didn't respond. Now, in hindsight she was just making conversation and being polite. My gut feeling already told me that there was no sexual energy that night we kissed after exchanging numbers. Also her friends were there and that gave her validation.She might have had a conversation with her girls: "see this hot guy I'm chatting with? And now he's txting me. Ugh boys!"
It's all to boost her own ego if you ask me.
Does it bother me? No, I learned a precious lesson to always follow my gut feeling. Which already hinted to me that this was a no-go. But out of curiosity I still txted her. You, never know.....

This is a little off-topic what I'm about to say. But to guys out there: don't waste your time on an ex. Like they say: An ex is an ex for a very good reason.