Girl too shy to pick up the phone?

Anonymous
This girl likes me and I like her but I've made things bad these past weeks so I sent her a letter getting to the point that I was sorry and she had said awww, that it was really sweet, that we should meet up and decide our options etc. She's quite insecure and timid when it comes to lads, we have kissed before though.

The weekend just gone I asked if the next weekend she would want to meet up and she said 'sure yeah okay x' and I replied the day after saying something, then if Saturday is fine?

She didn't reply and it has been 3 days so I assumed she didn't get the text. Her facebook status 2 days after was that she was saying she was getting an early night because she was annoyed and stressed and that she 'hates wasting time on people'. So I decided that asking her by calling her was better to show that I'm interested..

I rang her, but she texted back.. this is how it went:

her: 'you ring?'

me: 'yeah x'

her: 'What did you need? X'

me: 'wanted to call you to ask you about something x'

her: 'Text me. I'm ill so I sound dreadful.'

her: '?'

me: 'It's just to ask you something quick anyway ;-) low on credit but thought it better to say calling you x'

her: 'Go on then, ask me ...'

I rang her again.

her: 'I'm not answering lol, just ask me over text I hate phone calls'

her: 'felton?' (my name)

I'm confused, what should I do? I would have preferred to ask her through calling but she outright refuses and she is very shy in person with me. What could it be?
Girl too shy to pick up the phone?
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