No no no, thats plenty! Its just good to have an idea so we can give you better suggestions.
For that budget, you have plenty of options! I spent PLENTY of time as a poor college student so I understand.
The first ideas that popped into my head - a really nice hardcover book, maybe even a coffee table book...she doesn't need smell/taste to enjoy them. Of course with the new twins, she might not have time to enjoy them!
Personalized or non-personalized stationary sets. You can get personalized stationary at vistaprint.com - you customize a design, add her name, and place your order, and they are fairly inexpensive (you could get 20-30 notecards with envelopes for your budget). Teachers always have to write notes to parents, as well as personal notes, so this can be a great choice. Otherwise, you can go to a store like Papyrus and find a cute stationary set...everyone needs to write notes, despite the advent of email!
Things remembered is another great idea - a picture frame or other engraved item would make a great gift, especially if you have a picture of the two of you to put in it!
What about an ornament that expresses your gratitude? Assuming she has a tree, she'll put it up every year and remember how grateful you were. This one is pretty, or there are plenty more out there: