3 Year Old - Trouble Adjusting to New Baby

Are the grandmothers coming in and going directly to the baby first? Maybe you can have grandma come in and say hi and spend about 15 minutes with the old child before holding or coming to the new baby. I have 11 month old twins and a 3 year old and he is still having a little trouble adjusting. If someone says hello to the babies and does not acknowledge him, he gets upset and says "Mommy he/she did not speak to me". It will take some time, but she will get through it. Just remind grandma that your little one's world has just been rocked and she is trying to adjust and does not have the words or coping skills and adult does. Best of luck and Congrats!

LOL!!! I really have to laugh at this post because it happened to me. When my daughter turned 2 1/2 she went through this stage that she "can't like Mommy". It lasted till just 2 months ago. Took her a total of 9 months to get through it. I think it just may be a phase she's going through. She'll get over it. Just tell grandma to not take it personally and don't feed into it. Good luck!

ADDED

I think our daughter was doing this because she didn't want to share her Daddy with me. (I'm the working parent and my hubby is the SAHD) Perhaps your daughter doesn't want to share her sibling with Grandma. ;)

Does she understand the word "jealous"? Try talking with her about how she feels right now about all the changes and if that is why she is acting odd around the Grandmas. Discuss what she could tell you when she wants your attention instead of Grandma's. Model the language and when she is rude to Grandma then remind her that she might feel jealous right now but that does not allow her to be rude.
Also, have the grandmas pull back a bit and not try to engage her directly so much. Maybe they can start a fun game without her and let her approach instead. She might sense they are there to block her from bothering you...try to set aside time for your older daughter when the grandmas can help with the new baby so she doesn't see them as a barrier betw. the two of you. Just a thought...

This happened to me, but in my case I knew why. My in-laws came to meet the new baby and come to my 3-yr-old's b'day party. I don't know what happened, but my MIL started being really mean to my 3 YO. (My MIL is a mean person but I never expected her to be mean to her grandchild!) After a few days she started being nice again, but my 3 YO started being really mean to her! Didn't want to play with her, didn't even want grandma to talk to her, and honestly I didn't really blame her. I'm sure your case isn't this extreme (as I said, my MIL is a very mean person), but maybe the 3 YO perceived something as mean, or just sees that she is getting less of Grandma's attention? I asked my daughter to try to be nice to grandma until she left, and she was better after that.

Could she feel you are pushing her off on Grandma in order to have your time alone with the baby? This could easily be all about wanting Mommy not Grandma.

I'm sure you've done all this already but just in case:
-Have you asked her why she doesn't like grandma? Did grandma do something mean to her? Did she hurt her or make her sad? (you may be surprised at what you find out - i.e., she may be upset that grandma pays attention to the baby more than her, or calls the baby by a nickname that's been meant for your older daughter)
-Give her some time with grandma without the baby around, to help rekindle their bond; maybe have them go to the park together?
-Explain what's appropriate behavior, give a warning, offer a consequence and then hold true on that consequence by giving her a time out or temporarily taking away a privelige that she likes; really reinforce her behavior when she's polite and nice to the grandmas

Good luck and let us know how it goes!