my rat may have had a stroke?

Question
I originally bought 3 sisters from 'pets at home'. After 1 year, one of them lost a lot of weight and became really cuddly and wanting attention all the time, not sleeping or eating proparly. She died about 3 months ago. Now i have 2 left (little Ben and Yayo). I went to get Yayo out of her cage about a week ago and she looked different, she was wobbling slightly all the time and reached up onto her hind legs then fell over and got stuck on her back. her head was turned slightly to the side and her behaviour was odd, she also bit me for the first time.
3 days ago, Yayo came running out of her house on her hind legs, squeaking loudly and franticly and threw herself against the bars repeatedly then eventually collapsed, panting and squeaking, appearing to be in a lot of pain. we made her comfortable and left her till morning as it was 3.30am. in the morning she looked even more wobbly and sideways but was perfectly happy eating and wanted to come out to play. now i don't know whether its cruel to leave her as she could have another fit but to have her put down would be cruel too as she looks happy. what shall i do ?

Answer
What did the Vet say ?  I would not consider  putting her to sleep without knowing what is causing this.  It could be simply an infection that is throwing her balance off , which can cause inflammation on the vestibulocochlear nerve and cause her to lose her balance and act the way she is.  Antibiotics and sometimes something to calm her down such as liquid valium and something for inflammation are warranted after a thorough exam by a qualified Vet. I think she has a great chance of recovery once treated.