Kelly Creates! You can purchase sets of her pens in big box stores in the United States - I believe Hobby Lobby stopped selling them, but Joann's/Michael's/Harbor Freight still sells them because I see people posting all the time in the group that they went to one of those stores and found these and just had to have them. She also has practice workbooks. I purchased mine at Michael's on clearance but you can get it at Walmart, at least you can at mine. I'd definitely suggest joining
the group on Facebook as well, she does helpful videos and "boot camps" for learning new things.
The thing with the books is it's encouraged to practice the "drills" every day. Depending on how severe her learning disability is, this may or may not be difficult for her to do, but it's worth a shot. I, personally, have not been able to pick up the lettering - I have not practiced every day and I think I have the wrong pens because my letters just don't look very good. I can't get the "light/hard pressure" and thick/thin lines thing down right now, probably because I have not practiced very hard. But with a set of pens (I'd probably go with large brush for a learner?) and one of the practice books I'll bet she's on the road to learning in no time.
There's also a few free things out there for iPad lettering practice, if you'd rather go the free route at first. I can't remember the place I saw them, but I do know that I just googled "iPad free brush lettering" or something like that.