The John Lewis machines are great, I may be wrong but I think they are Janine build which means you can add different feet to them.
The only downside to the cheaper range of machines, and this will be the case of any of the budget models, is that the throat is very small. Essentially this means that trying to quilt a large quilt is very difficult, but should be fine for baby and cot size etc.
Quilting fabric choices now are amazing, there are so many great online shops these days. I'm not sure how tech savvy your mum is, but there are an awful lot of quilting blogs out there, Red Pepper Quilts is lovely, fresh and modern but a vintage nod.
Instagram is also great for inspiration.
If she likes making clothes there is a massive resurgence in Indy sewing patterns at the moment. Again, Instagram is great for looking at what's happening in the sewing community.
Aldi and Lidl are also good for sewing bits and pieces, worth keeping an eye on their special buys.