Hi E.,
It's a good thing they're so cute at two, isn't it? Relax in the thought that this phase should be over by the time your baby is due in March. :)
I don't think it is mean to close her in her room when she is misbehaving because after all, whenever we lose control, we want the privacy of our own room to cry in. We are all allowed to express ourselves, just not violently or at the expense of others. Later on, you can send her to her room to regroup and change her attitude, which would be consistent with how you handle it now. The problem is, it's ineffective.
Try putting her clothing in her lowest drawers and telling her to come out for breakfast after she has dressed. Let her know she can ask for your help if she can't get something on herself, but then you can leave her room and let her do what she will. You then wait until she is dressed before you serve her breakfast. I wouldn't put a negative spin on it like, "Not dressed, no breakfast" because she's willful and will rise to a challenge by not eating breakfast. Just relay it as a courtesy to her that you will be more than happy to wait and serve her breakfast after she has chosen her clothes and dressed herself.
Do you think that might work, or have you tried that already?
Good Luck.
Just remember they are all phases... if you love it, video tape it. If you hate it, enjoy the knowledge that it is just a phase; it will be gone soon.
D.