Some of these Alexis theories are kinda out there and some aren't even remotely believable if you go off of the information that is given and hinted at in the game. Most of them are just pure speculation based of tropes seen in other games, shows and movies. There is nothing in the game hints at Alexis being married/in a relationship already, having a sugar daddy or having a kid, keep in mind she is a 20 year old college student with a job as a bartender.
Now my own theory on Alexis is all based on things that are shown or said in-game, and thats not to say that i think im 100% right and every other theory is dumb/bullshit or anything, this is just the theory that makes the most sense to me with the information that has been giving in the first 4 episodes.
Okay here we go...
Alexis is Layla's sister. Alexis has the same complexion and hair color as the sister when she is shown in Laylas room (her sister just came out of the shower so her hair seems darker than it actually is, but she is still a brunette). Conveniently Layla says she has a sister but she is not named ever and the one time she shows she has her back towards the camera. It is revealed that it was a female who interrupted MC and Alexis in the shower, was it Layla? i think so. Alexis is also the brunette girl who was present when MC confessed his love to Erynn by giving her a flower. hmm who seems to have a weird thing about flowers? oh yeah Alexis does, she talk about not being given flowers ever on the plane and almost cries when MC gives her flowers on their date(if you choose to give her them) What is the thing Alexis is afraid of telling the MC? Alexis was/is friends with Erynn since she was the brunette present when MC confessed, Alexis had feelings/felt bad for MC when he was rejected and she was directly involved in the event that ruined MC and Erynn's relationship, she obviously feels terrible about that. She also knows MC's address, how? from Erynn of course. MC's mother? thinks she looks familiar? probably because she has seen her hang out with Erynn back then or recently.