You should also be able to tell if she is pregnant instead of just a bad case of worms by checking out her nipples. (if she will let you). By now the fur around them should be thinning out at they should be more pronounced and pinker. Compare them to Tinky to get a comparision.

If/When she has her kitties - its nice if you can start to give them human contact from an early age so that they can become more social and friendly.