It's really difficult to recommend without knowing how much your mom has in mind to spend on it. If your mom is a quilter/sewer, maybe she has an idea of what prices are these days, but otherwise, she may be in for a shock.
I would stay away from computerized Singers. I bought one 5 years ago and when the main circuit board encountered a glitch 3 months after I bought it, the warranty covered it, but it took many weeks to get the part, and the shop was an hour and a half away. It has been a good machine for me since then, but that was not a pleasant experience at the outset. Before you buy any machine find out where you'd have to go for service. Expensive machines should be bought in a store near you that offers free lessons as well as technical support. Not all authorized dealers have warranty certified repair personnel.