My cat was meowing at nothing, after I called her name she stopped walked over behind the couch and started meowing again. Is she sick?

Cats can become vocal for lots of reasons, some of which are behavioral and some health related. Only your vet can truly tell if the cat is sick, but be alert for changes in her eating and drinking habits, litter box offerings, and activity levels. If these are altered then get her checked. Also older cats can become more vocal if they have gone deaf, so you might want to test her hearing (although she did come when you called.) Alternatively, some cats meow at nothing because it got your attention last time, so be sure she gets lots of fuss and isn't bored.