Our sewing guild has this happen all the time. We thank the donors and tell them the fabric will be used to make our charitable items and also shared with other groups who sew for the homeless and shelters. I don't think she's looking for a return gift.
All of us sewers periodically go thru our stashes and clear out those fabrics we are not going to use and donate them to the churches and quilting guilds.
If you have some time and can make her a small gift, that's great but I don't think you should feel guilty. You might let her know from time to time what the fabric was used for or even show her some of the items. I'm sure she will be very pleased to know her fabric is going to a good cause.