P.S.
Check for MOMS, MOPS or any other type of 'play groups' that are in your area. Also, is she involved in your pregnancy? Does she go to the doctor with you, shopping for baby things? I remember my first going through some changes at three and I was also pregnant. This is (and will continue to be) a big adjustment for her. Make sure that you talk to and listen to her. Sometimes all they need is to know that you "get it". Something as simple as "I know you are mad because...but you...." can do wonders.