Can't give a definitive take on this...
Lexi she knows the entire picture, BFF wants some, so does baby sister, she can't be too mad if the MC scores with either after the "break up", maybe she'll voluntarily step away from the "contest" if you do her sister(she mentions she can't lose Layla too).
Erynn... she's mad jealous, but... she got madder at Lexi for being a "backstabber" than she did at the MC(in fact no problem at all here) for scoring with "some girl".
She gave a pass once, but now everyone is familiar with the connections, she might break it off if you "go back to the well".
Nikki has been totally mature thus far, never even asked "what you been up to" in the time they spent separated... maybe that will change but i don't expect it to be honest

, whore away and she'll pay no mind(i think), just don't impregnate any chicks

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Layla does worry me, in 6.0 she already storms off if you tell her exactly how well you know Alexis, i get the feeling she won't take things lightly, she's the youngest of the bunch and it shows, if you stopped seeing Alexis maybe there's calming her down, but if you (again) go "back to the well" i don't see it.