I've had it. First episode was actually on a
DCL cruise. That first time freaked me out because I was on a ship and didn't know what it was. However, I've had a few flare ups since then and now I know better what to look for and how to handle it.
Anyway, antibiotics will usually take care of it and it takes about a 7-10 days or so for it to completely clear up---although after the first few days it isn't as painful and the swelling goes down enough that you can walk without noticing it much.
I haven't had any long term effects (knock wood) so far...except additional flare ups. To this end, I call my doctor at the first sign of redness or warmth in my calf and get on an antibiotic immediately.
The first repeat flare-up, I waited a day or so from the time it became tender until I noticed the redness (thinking maybe I just bumped it or something) and it took a few days from starting antibiotics until it turned around significantly (although fewer days than the first time). The second time, I called at the first sign of tenderness and we nipped it in the bud before any swelling/redness. So lesson learned---stay on top of it!
As for prevention, my doctor suggests wearing surgical stockings (especially when you are going to be on your feet or walking a lot) and to protect your feet/legs from cuts that might cause infection. She suggested a thick cream to eliminate dry skin (which can be an entry point for germs) and to use antibiotic ointment liberally on any cuts/abrasions you do get.
I don't like the stockings----but wear them on planes and whenever I am walking a lot. I found some skin colored ones that aren't quite as obvious. Yes...one can see it isn't my own skin, but they don't stand out like the white ones do. I make a point of wearing them if I think I am about to get a flare-up to at least keep the swelling down.
So....your mom will always need to be diligent---but, so far (knock wood), my experience is that once the episode clears up--I don't have much of a long-term issue except good preventative care (which isn't very difficult). I think my first episode was the worse as much because of my panic about the unknown of what it was as anything else.
Good luck!
P.S. I should note that my own dm is prone to cellulitis so you might be one day too. Also, she had a much bigger issue with it when she was younger (about 20 years ago) because she waited MULTIPLE DAYS before getting treatment as she thought it would just clear up on its own. She did have permanent scarring/cell damage and that leg is always a little swollen. However, that was 20 years ago...and without getting immediate treatment. Now we all know better and it hasn't really affected her quality of life except she has a little trouble buying shoes that fit well on feet that are two different sizes. Again, 20 years ago......