I agree with Jade. If it is only occasionally and slight I wouldn't be concerned. If it happens frequently or repeatedly, she may have digestive or dietary problem that is causing over production of stomach acid.
Hi and welcome to the forum. Does zsazsa do this often? It's probably just bile - I've seen my cat do this after eating grass. If this is happening just now and again, I don't think it's anything to worry about - maybe a little tummy upset, but let's see what others have to say.