Hello again. I think I would have done the same. Rescuing Mimi means she now has a nice loving home for the rest of her days. Although I know you are aware it could only be weeks or months. I am not sure if you can, but after the grief we had after Charlie, I decided I wanted to have two hamsters. It may sound selfish, but I was being pragmatic. That if one dies - you still have the grief, but you also have the comfort of the other one needing you to care for them. Because one of the hardest things about the loss was suddenly not being needed to do the care any more.
Although it doesn't guarantee anything - ie which one would go first, or even both fail around the same time, but generally if you have a younger one as well it's more likely they would live the longest.
We got a robo as our second hamster. He is happier being left alone in his cage but will talk through the bars
I never did get to tame him as he was so nervy and he really does seem to prefer being in his cage mostly, although has had the occasional out of cage time, but they are very nervy little things. A nice environment in his cage keeps him happy and he uses both a wheel and a saucer and loves those. He is also a real tunneler and digger (I think robos do tend to be) but currently has a labyrinth house so uses that.
Regarding the teeth - an older hamsters who has not had adequate hard chewing, may need the teeth burring at the vet under a quick light anaesthetic. I was told that is what they do now rather than clipping the teeth but it may depend on the vet.
She would need a vet visit and her teeth assessing. The vet will be able to do something, and if she ends up virtually toothless she can do well on a soft diet. They have probably got too long so she can't eat properly.
Charlie had this when he was just over two and his teeth had to be clipped. He ate very well and chewed fine after that. But when they're older there can be other reasons they're not chewing hard things - eg toothache in the back teeth or arthritis in the jaw - so in avoiding chewing hard things, the teeth do get too long.
You will have to see what the vet says but I doubt it would be monthly trimming - just keeping an eye on to see if they get too long again.
Our two year two month syrian appears to have lost his top teeth now (or maybe just worn down), but is eating fine - even so I am supplementing him with some softened food just in case he isn't eating properly.
The vet would advise on that as it's tricky- you want them chewing/eating hard things to keep the teeth in trim, but you also need to make sure they get the nutrition. I put both out - hard food and 3 or 4 softened science selective pellets separately.
I don't think it sounds congenital if she has got to 18 months - she would have had problems before now. See what the vet says - the vet can also clip her nails while she's there.
Again older hamsters do seem to get nails getting longer easier, but you probably know you can help keep those trim by having something rough under the food bowl or under the water bottle - eg a terracotta plant pot base. I have a rough granite tile under the water bottle (which also helps soak up any drips!) and not had a problem with nails yet.
From the sound of it the pet shop vet is doing her teeth before you collect her, is that right? It might be worth asking if you can just take her anyway and take her to a vet yourself - then you get to choose a vet. An exotic vet tends to know more about hamsters.