If you have a dealer anywhere close to your home maybe you could pay them a visit. Find a couple that are in your price range, buy her a gift certificate so she could go in, try out the machines and choose the one she likes best. The dealers never ( or seldom unless having a big sale) have the prices on them. They would know which ones you were looking at and steer her toward them.
Another ( perk) to working with a dealer is " new owners classes" which are free and teach you how to use all the features of the machine, along with local service and trouble shooting. If that (local) is available you could choose a machine yourself but talk to them about her trading for something different if she likes something different when she goes in.
I would start at a dealership and explain the situation and talk about options, budget, services, ( my janome included 5 years of free cleanings)