I'm sorry, but I feel that I have to put in another 2 cents worth in!!!
When she text you that she does't want money and that you are not a customer, I have the impression that pride or what the Thais call "face" has crept into your relationship. You must remember that these girls are people too and have feelings like the rest of us!!
To tell her that you will pay her the next day (as if she is some sort of supermarket) would surely put her nose out of joint and she would rather lose all that money than have to admit that she was stupid to trust that you would do the right thing by her. ( be it pay her or take her away from the bar)
An example from my own experience....
On one of my tours, I ended up with the same girl for 6 Weeks!!!! Her looks were nothing special and she did not even treat me like a king (which I deserved!!) but there was something about her that made staying with her very easy. (she, also, had not been in the barscene very long)
Anyway, about 3 weeks into the relationship she suddenly comes out with the idea that I should no longer pay her for staying with me ( I was paying her on a weekly basis).
I refused to accept this and went on to explain to her that I could not and would not offer her any sort of long term relationship due to circumstances outside my control.
I took her from Pattaya to Phuket to Ubon ( to see her family and for me to do a visa run) during which I paid for everything. So, like your girl, she was not out of pocket for daily expenses.
In total, I paid her (directly) something like Bht 40,000 and when we got back to Pattaya she also went back to the bar to collect her wages, LD money etc. At this point I found out that she had made arrangements with the mamasan that she would pay the barfine herself ( if I had known there was a problem, I would have offered!!)
To put an end to this story...... Her best friend told me later that by the time she had paid the barfine, repayed loans to get started in the business and sent money to her mother, she ended up with Bht 2,500 in her pocket!!!!
I have made this long post, not to berate you, but as you are a newbie, to explain that there are ALWAYS more things going on the lives of BGs than you will ever know about.
So please, pay the girl, in the nicest way you can think of, and you can both go on with your lives after having learnt something!!