Being a musician myself, I can totally understand your desire, and your daughter's desire to practice, practice, practice!
A few things to consider....
1) Sound bounces off solid surfaces. The more soft surface there is, the less the sound will travel. That being said, hang as many clothes in the closet, take a few clothes pins and pin the music to the clothes, and have her sit in front of the open closet to practice.
2) Practice time doesn't have to involve an instrument! Reading academic journals, clinician research on playing techniques, listening to masterworks while reviewing the conductor's score listening for your instrument's part, OR reading music for dynamics, breathing, and other detail are all great alternatives when you can't have an instrument in your hands.
3) They DO make clarinet mutes, just Google and see if you can find a set in your budget!
4) You can make a very inexpensive practice cubby out of the tri-fold cardboard display boards (think science fair display) and quilt batting. This is an option of you are driving or will have a vehicle while you are there.
5) Contact a local music store or University or College and see if an instructor would be available for a few hours for a master class. A few hours of practice on one afternoon with an excellent musician could be better than an hour of practice every day! For $100 or so, your daughter could have a wonderful experience and go home with food for thought and additional skill. The more professional musicians she works with, the better her ability to take direction and artistic critique. (Often a major hole in the preparation/education of musicians!)
6) Finally, they do make an electronic instruments (yes, even clarinets!) which can be used with headphones for 100% silent practice!
I hope this was helpful or at least thought provoking!