pregnancy assumptions:
Zoey? no, because if she's pregnant by MC that would be a problem that Mc couldn't wash his hands of, and if she's pregnant by someone else how on earth would she be palatable to MC? an ex coming back pregnant?
Bella? would make sense, but she just had her (useless) flashback, unlikely to have another one in the next chapter
Lynette? would be the most painless solution but it would seem strange to me that an image from Lynette's diary would be given in the middle of the narration as a preview.
an LI? impossible because the scene happens anyway.
that it is a secondary girl is the most likely hypothesis, and that Mc is not the father I would say for sure. so I would bet on a girl with whom MC has not had sex and is not expected to do so, Ashley would be too dramatic for Derek, Daniele and Wendy in my opinion have already faced and overcome this danger. I would say either Arieth or Sally