Second vote here for Harpmaker's Student model. I've been messing around with dulcimer for nearly 40 years; played hundreds of different instruments, and IMHO there's not a better dulcimer out there in that $100-$150 price range. I own one that he slightly customized for me a couple years back. It's my 'go to' general purpose dulcimer. Also, he has a trade-in policy if your sister eventually wants something even nicer.

Hey, Kim! David Lynch's Sweet Woods student model is $125 and I've heard nothing but good things about it. Dave's a member here and so is his sister (folkfan). You can see a picture by scrolling down this page:

http://www.sweetwoodsinstruments.com/dulcimers.htm