Don't deal with her outside ebay. If you were unwise enough to partiaally refund outside ebay she could still open a SNAD case and get a full refund despite you already having partially refunded her.
The fact she has even asked tells you all you need to know about her.
Furthermore if she doesn't want to deal through ebay it could be because she has been so dodgy in the past that she has been banned from opening any more cases with ebay, which would explain her wanting to deal outside ebay.
