I would do jewelry, as well. Depending on your daughter's taste, you might want to get her a bracelet or lavelier necklace or a dangle for her badge. Flowers are nice, but they don't last; give your daughter something that she will always remember her initiation day. If I had a daughter, this is what I would buy...
http://www.pibetaphi.org/fusebox/htd...000-1201730407
We never did gifts for bigs, but a nice card from the initiate's mother would be a great touch. If you really feel a gift is necessary, maybe something nominal like a Pi Phi picture frame.