I didn't write to her as it seems like it wouldn't do any good (She already relisted! And gave me barely any time to reply before she did). But I left her this NEG:
Non performing seller. Won for £10.50 but told me to pay £45 or she wouldnt sell
She now has the enviable feedback score of 33% I also reported her using those links Lee69 provided. Hopefully she will get kicked off ebay soon!