I think that cash or a gift card for somewhere where YOU'RE CERTAIN she likes to eat/shop would be equally appropriate options. Try to get lots of people to chip in.
I provide our secretary with a complimentary dinner for her and her husband at her favorite restaurant. I agree with others that cash is nice. But there's a personal touch that is missing with just giving cash. Our secretary usually will mention at some point during the semester how she and her husband went to x restaurant the night before and really loved it. When I give her the certificates to go back to that same restaurant, it shows that I was listening when she was talking with me. That little bit of an extra personal touch, to her, is priceless.
To her it's priceless or to you?
I'm not agreeing or disagreeing, just wondering how you know this is better than cash from her perspective if this is what you always do.
Someone recently gave me a gift card to my favorite salon. I found it more meaningful than cash. First, I like to support the small business owner there. Second, it shows that this woman listened to me--I don't even remember talking about it. Third, the idea that she went down to that salon just to get card means something more than withdrawing cash from the ATM. Fourth, it's more of "gift" to me. Had she just given me $25, I might've felt guily about indulging in salon products/services rather than using it on something.
But don't get me wrong--I love getting cash too.