$45- $50 would not be unreasonable. you should talk to her before she does it- .... 'what would you charge me to do this?'
if she says - 'oh-nothing'
then go with the gift card or maybe a card with some $$ and a gift card-
if she does give you a price she thinks is fair- well- problem solved...
these things should always be agreed upon before the work to avoid hurt feelings