Hi, well I do have some experience here
First I would say make sure that you choose the right place, and don't just follow someone else's suggestions. The first place we used was totally wrong, we discovered afterwards that they had no dementia care! This was because we kept being told that all FIL's symptons were just old age, and we knew this wasn't right. We should have followed our own instincts!
Some counties fund respite, some don't. Even when they say they do, they won't always fund a home if they don't agree its the right one!
Once you have found the right place, and you do get a feel for this, be positive and stay calm. Your feelings will reflect on your mum and if you are very anxious so will she be.
We gave the care home a very detailed report on FIL's normal daily routine and listed his dislikes etc, including what time he likes to get up, how he reacts on rainy days etc. The staff should then be prepared and can watch out for any triggers and avoid them. We also sent favourite foods in case he didn't eat what was provided, but these were not necessary
We also gave him a sort of calendar with a count down to coming home and the staff used this daily to reassure him.
I had reached the point previously where we thought we would never have good respite but this last time we did! But, for your own satisfaction, you do need to be sure youself that you have done all you can.
Good luck x