D.P.
I believe there are kids books at the library about this subject. Taking her to the ultrasound is a great idea. My first was about 2 1/2 when my 2nd was born. They can understand a lot, but it is not something they will think about all the time. So the ultrasound will show her the baby in your tummy and you can talk about it once in a while with her, but as July gets closer you can talk about it more as it will be more real to her as it is only a short way as compared to months. She will probably also like going through the old baby stuff with you to get ready for the new baby and also like feeling your tummy when the baby kicks. Hype up the whole big sister aspect of it and dont flaunt new stuff that you buy just for the baby so she doesnt get jealous. Extra TLC before the baby comes will make her feel secure too.