I think it sounds fine, except I would be definite that you can't adjust them so she won't ask you to try anyway.
I retyped it with corrections since you complained about your English.
You can use it if it would make you feel more comfortable communicating with her. I do think what you typed is perfectly understandable though. (buyer doesn't have any paypal fees, so I left that out)
Sorry that you're not satisfied with the flower beads.
Unfortunately, I cannot repair the beads, and I can't adjust them as you require.
I'll be happy to refund your purchase and shipping costs after you return them to the address below.
Sorry again for your disappointment.