Hi Marie, and I'm so sorry to hear about your mother. Of course the move was a big shock, as you say. Anyone, but especially someone with dementia, needs time to make the transition.
I don't want to sound heartless, but I agree with the advice not to visit for now. Maybe a few days, maybe a few weeks; it's hard to say and everyone is different.
I would definitely ask the staff at the care home what they think and follow their advice on visits. Even if you are not visiting, you can be in touch with the staff as often as you like for updates and information. Remember that what you see when you visit, is often not what the staff observes.
When you do visit, she will likely protest about being there, or want to go home, or both, or maybe not at all. Don't feel guilty if it is upsetting and you do only a short visit. If you get upset or overwhelmed, try a short break (I make a lot of trips to the toilet; she can't remember I just went five minutes ago!) or a distraction--biscuits work for my mother. Always have an exit line/exit strategy ready and don't be afraid to implement it and make the exit quick, not drawn-out. If you're really unsettled, phone the staff after you leave to see how she is.
For what it's worth, my mother went into a care home in February, after living alone with no help and refusing assistance. Of course, to her, there was no problem with her living alone. (Never mind not eating, not bathing, not doing laundry, not cleaning, ancient food in the fridge, not being able to pay bills, living in squalor, the list goes on--but no, no problem, she was "fine.") I did not visit for at least a couple of weeks, as I was persona non grata and she was not, ahem, kind to me. After about a month, she began to settle a bit. Almost four months on, she is much more settled. I was told it would get better, but did not believe it. It did get better.
Please hang in there and remember you can always come here for advice or just to vent. Nobody here will judge you. Hang in there!