It's funny that I have watched this many times but I just noticed what you are talking about. I always assumed that Chico was talking to Sonny, but if you notice she is looking in the direction of Vanessa when she says something like "Yo baby, if you ever need someone to talk to, I am up here for you." Maybe the audience laughs because Chico is trying to get at Vanessa, and Vanessa doesn't want any part of it.
nigdss says the part exactly right ~ have it on DVD and watching it now and always laugh at that scene myself. Cuz it basically is stereotyping at it's best ~ Tyler Perry is showing us how prison is always showing a man wanting to get w/ another man due to no females around but this time vice versus due to a woman's prison and no men (besides the guards to go after). So Chico only has a few choices and Vanessa happens to be the new catch so she tells her that she is there for her. Of course Vanessa is like 'No...No...'