For about 24 hrs she should be Ok, Misa my big boy wouldnt go out last night although he was busting and used a tray in the end, actually two!
If it goes longer than that, keep a very good eye on her and by 48hrs plus a vet visit likely to be needed urgently. She should be by then squatting and trying to go and she will need help.
Hope she decides that litter trays are the option