I agree Melissa S needs to go! I haven't seen MTB3 but her whole 'I'm the gril next door' babble annoyed me, considering I thought she looked somewhat skanky to me. I can't explain it, but I see an underlying skank lurking with Melissa S.
On the other hand, I adore Chelsea. She's so cute! She reminds me of my friend, loooks and personality-wise, so I'm rooting for her.