I have many years of experience of nervy cat with bladder issues - have never had antibiotics but there has been a lot of wee and at worst with blood.
One litter tray is not enough. As a minimum you need number of cats + 1. Even if you don't have that many all the time, first hint of trouble the bins come out.
Nervy cat needs to feel less nervous - hopefully she responds to Feliway so stick Feliway everywhere.
We always have a bottle of Metacam ready, as if you are already nervous, and then your bladder hurts, you are just going to be worse. So again, first sign of trouble, start the Metacam.
Wee needs cleaning up with a pet odour cleaner as standard cleaning doesn't eliminate the smell for cats so they keep going back.
Other things you can do to prevent issues are up the fluid content of the cats diet, there are urinary dry foods which are supposed to prevent it and they do seem to work, urinary health capsules (we use Vetpro Urinary) also seem to work.
Lastly just get the cat happier. Lots of play and interaction, stuff for the cat to do like towers and tunnels, more time outside if they go outside. Basically stuff that is exercising their brain rather than sitting at home being scared of their own shadow.