I agree. How would she not know? And u said twins I think. You have to be showing more. But I think she will be okay. Its new babys. There going to be fun
I'm kind of confused as to how she wouldn't notice. I'm sure there was some planning and some baby items around the house? 3-year-olds notice a lot.
If you're due soon preparing her is a great idea. There's many books out there to help prepare small children.
you can get some books out of the library or from the book store about becoming a big sister. Unfortunately, I haven't been able to find any really good ones, but several are OK.
Since she is 3, I would definitely get her involved in setting up the baby stuff asap, considering you're due so soon. Let her pick out some outfits for each baby (and herself!). You can also get some stuff for a special baby doll she has so that she can take care of her babies while you take care of the twins. My daughter (2) received a doll stroller, swing, high chair, etc... a few weeks ago to help prepare her. If you help her feel important and special, then she may respond better.
Try to get her excited and if she sees your belly growing even at 3 she knows something is going on. I would just explain that this is her baby too. That way she will feel a part of everything that is going on with (are you having a singleton or twins???) the baby (s). Just sit her down and explain the best you can! Good luck!