I use Deramores too and I have always found it to be a really reliable website. Personally, I like bamboo needles because I find them easier to handle and I find plastic ones quite tricky because the wool sticks, but everybody has their own favourite. I agree with musical66, I love knitting but it can be tricky when I’ve got cramp or dystonia or my hands aren’t that coordinated so I quite like making smaller projects that I can finish - though it depends how long it is since your mum has knit because some smaller clothes and toys can be fiddly. If your mum hasn’t knit for a while, it might be easier to start with some larger needles (6mm - 8mm maybe) and thicker wool because it knits up quicker and it’s easier to handle. Depending on how long it is since your Mum has knit, a straightforward scarf is going to be the easiest thing to get back into knitting with but if she’s a pretty good knitter, a sleeveless top is a nice project or a small poncho for a child maybe. Another good project is making squares which can be sewn together to make a blanket, throw or poncho. This works well because it can be as big or small as you fancy making it and you don’t need to buy all the wool at one time as long as you make a multi-coloured blanket. You can even order a couple of balls of wool and some needles to start with so that you haven’t spent too much money if you need to rethink. The same also applies to making dolls clothes and toys because you don’t need much wool.
Lovecrafts is another good site to look at as is Hobbycraft and both are reliable.
My last tip would be to get wool that does not split easily and is not fluffy for the initial project.
I’m not the best knitter so these are just my personal tips but I know there are lots of proficient knitters out there who will have really good advice.
My last thought would be that if you get stuck at the moment when you can’t get help from a knitting shop or club, there are any number of instructional knitting videos on YouTube which break down everything you could possibly want to know about knitting into easy to follow stages. Hope you manage to find something your Mum enjoys. Jx