It seems like you did most of the work, and you just want to thank her for her assistance. If she is a friend, she may not want to accept money, but a gift card is more like a "gift." Based on what you have written, I think a $100 gift card would be very nice. I know I would be very appreciative of it.
Best wishes and good luck with the investment!!
Dawn M Jett
Designated Broker/Property Manager
Vista View Realty Group