Diane as currently characterized would have absolutely no interest in being a beard unless she was completely free to have sex with other people, which sorta defeats the purpose. She could cover for the occasional parental visit, but that's about it. An occasional threesome partner? Maybe, but we don't know how she feels about women.
Alana's just too casual an acquaintance (thus far) to be elevated to narrative importance, plus she's interested in someone else.
Lisa remains an unpredictable wildcard.
Adriana is married. She's of no use in this regard.
Which leaves Sandra as (so far) the only reasonable
Haley+1 option that Ptolemy mentioned. I'll admit that Sandra being okay with Haley feeling her up was, at least to me, a more jarring surprise than the one that everyone's complaining about.
If there's going to be a "bad" end (which I'd define as a break in the relationship between Haley and the MC, whatever that relationship is) it'll almost certainly be based on there being an insufficient number of
"Haley points" to survive the confrontation and/or trauma over Klaus. If the devs were
really good about
allocating points then the threshold number would be exactly the number wherein the MC expressed care for his sister but not require him to have made sexual advances, even though that happens anyway. That allows one to play the game by accepting that the situation turns sexual due to Haley's pursuit but to leave them as twins who love and care for each other even if their sexual relationship ends, which I think would be a logical alternative ending.
I think these are the only endings justified (thus far) by the text:
If that's how it's going to go, people should get used to short updates. Adding or removing either
Haley or Sandra from the story is a
serious branch, especially because
the twins would be unlikely to keep living together if things went to hell. Although, now that I think about it, if
Haley moves out or orders the MC to move out there's no real necessity to continue the story beyond that point, given the title.
As usual, this is mostly speculation and there may yet be some twists.