It sounds like she wants to be around you and the baby, so much so that her desire to be near you/get attention from you is overiding her discipline. I have that problem with my dog too (a black lab/beagle mix). Especially when Jack was smaller (she's not as big a fan now, since he can chase her and he pulls on her, hits her, not in a mean way, he's trying to pet her). I wouldn't say she's really jealous, just more craving your attention. I have found that spending some extra "Darla time", where I play with her, pet her, let her give kisses, etc. helps. And yes, sometimes I still just have to resort to raising my voice. Also, if you are protective of the baby when she's around (which is a normal reaction!) she may feel that she's been replaced. Which she has, so you might want to try letting her interact with the baby more (if you don't already). Let her be near the baby while you're holding her, let her give the baby a kiss or two, stuff like that. Trust me, in a few more months, she will probably settle down. And remember, at 2 years old, she's at the tail end of puppy-hood. She needs lots of interaction and exercise, especially being a lab. I used to put Jack in his ExerSaucer and play fetch with Darla. He got a big kick out of it, and she was happy she was getting exercise and attention. Now he plays fetch and tug of war with her, now she will being him her toys to throw and play with him. (She is much gentler at tug of war with him than she is with us!)Darla was 4 when Jack was born, so she was a bit older, but she had a very similar reaction, since at 4 years old, she was still a bundle of energy. Actually, this year, at 5 years old, she's STILL a bundle of energy. But now she has a partner in crime. :-) I think pets are a great thing for children to grow up with, so just be patient and extra loving to your 4 legged baby and hopefully you'll see some improvement. But I will say, if your dog is anything like mine, she will always have her naughty moments, they just get much less with extra attention (and the occasional firm command).
M.