well, she isn't going to be always sewing on heavy, thick fabrics unless she really enjoys working on denim. I made a quilt for my son out of his old jeans and corduroys and yes, it was impossibly heavy - I ended up just tying it, rather than trying to quilt it with a machine (didn;t even contemplate hand quilting) I have a Juki and it probably would have powered through that quilt, but I didn't have it then....so for a new machine I would suggest a Juki, either the quilting or Exceed models. (both around your price point) However, if you have to time to peruse Craigslist you can probably find her a good vintage machine - either a Singer model 15 or a Japanese clone of singer 15 for under $100 that she will be able to use to finish the jeans quilt...it will be a simple, very strong, powerful straight stitch only mechanical machine that she can use for all her piecing and quilting if she desires...or you can still buy her a modern machine with "bells and whistles" like a Juki to go along with the 15 - most of us have a "few" machines to play with:-)
Joann