I have to second Ruth6:11. I realize ECT is rare and is used as a last resort, but when you're at that point it can literally save your life.
In my 20's (I'm 35 now) I had a manic episode that got way out of hand. I was fully psychotic, being treated with every med they could come up with, and getting worse by the day both mentally and physically (not eating or drinking, hallucinating, thoroughly deluded, etc.). I was responding to no treatment offered, and as I understand it, the longer one stays psychotic with the brain misfiring and establishing new, bad neuron pathways... the harder it is to come out of it and the more permanent the damage is.
The docs told my husband that if I continued the trend, I "may never come back" from the crazy dreamworld I was lost in. So they did a series of ECT treatments. It jarred up my brain and gave it a chance to return to normal function, re-establishing new neurological pathways. It wasn't easy (for my husband, especially) but we're glad we did it.
LostandWorried... yes, it does affect memory, at least it did for me, but not in a way that should cause you despair. I don't remember ANYTHING about getting the ECT treatments except the very last one. I remember coming to that time (they sedate you) and having the most awful headache. And yes, I lost 1 - 2 months of my life memory-wise because of it. I still remember much of the hospital experience, but the post ECT time at home is very fuzzy. Even today I can look at pictures of myself feeding a camel at the zoo and have no recollection of being there. It's wierd, but a small price to pay.
The ECT didn't have any effect on my recollection of people or give me an amnesia type experience beyond simply having lost those few weeks. On the other hand, I do seem to have a little worse memory than before, both long and short term - just more "senior moments". I also feel that I'm not quite as sharp as before, and work a little harder now at focusing and problem solving. But the doctor suspects this is due to the neurological pathways that were broken beyond repair by the mania, and possibly not the effect of the actual ECT treatment. But I'm "still myself" and I'm just grateful for what I still have! If your mom is psychotic, I wouldn't delay in accepting help.