i haven't been able to do that as lexis trailer burning down requires the event for them to meet in the nightclub and sadly, i dont think you can run two home harem questlines at once
According to the rules of the walkthrough instructions:
The family harem can only host one girl at a time, so when you want to take Lexi to live at home, it depends on how many cohabitants you have at home at the time, and you can ask for their consent. That is, if Minami has already moved in, you can Have to ask Sasha, Bree, Minami.
The Samantha route is very easy to control the progress. For example, if you want to find Emma, as long as you don’t meet the love point after the wedding, or avoid being at home on weekend afternoons, Sam’s tasks will be suspended, and you can have enough time before becoming her boyfriend Time to communicate with Emma. Similarly, you can also control freely if you want to suspend the progress of the family harem, etc.
Lexi's Trailer burned down:
1) Tell her "Of course you can come!"
Mike decides that he needs to help Lexi, but he has to speak to his housemates (including Samantha if she's already part of the Home Harem) before.
Here, as long as you complete Samantha wants to know the truth, then snub Sam, and avoid meeting Sasha and Bree at the same time, you should not trigger the harem-Samantha. You can choose who will complete the harem mission first, Minami or Lexi.
I'm not sure if after Samantha wants to know the truth, Sam's Lesbian Points will be raised to 50 and locked immediately, if not, you can also control it from here.