You have to dismiss Mai-Lynn from your household. She will then help her father, adding more income to the garden. You can still recruit her to your household later if you want.
Ok. Just tried that, and it works, but it seems... pointless?
Like, it's an income boost, sure, but you lose the boost she provides your garden(s). I guess it gives a special utility to her for the people who don't have gardens at all, because they turned all their land plots into workshops or whatever, but if you aren't going down that route I'm not sure I see the value, because rehiring her eliminates that revenue stream anyway.
Which I honestly find kinda weird. You can get Caitlin back and still be making money from a clinic she no longer works at, so this seems like a half measure in some ways.
Also, on the subject of Caitlin, I think it's kinda weird that you have to free and dismiss her to get the clinic in the first place. You don't need to free Nicole to get the newspaper up and running, and even if Caitlin's freedom was a requirement to get it, I feel like it'd make sense to still be able to get the clinic if you gave her freedom by marrying her.
I dunno. Just seems like there's a weird imbalance in the special effects and costs of certain girls with unique jobs/traits.
Mai-Lynn: Either takes up a job slot that you can only give one person and a plot of land to buff your food, or gives you an income boost if you've done her quest and kicked her out of the house, and thrown money at her father.
Nicole: Has a completely unique job, but the job requires you to invest in one of your rooms.
Caitlin: Complete her quest, kick her out, invest in her clinic enough, and you get a passive revenue stream while still being able to have her work for you.
Rebecca: Give her a unique title and she buffs your investments.
Aria: Literally just has to exist.
I'm not saying that any of these approaches is necessarily superior to the others, but it feels odd to me and a little unrefined. Like if someone wasn't sure which way to approach this system and was trying different avenues of design (very possible), or like each system was developed by a different person, and they were all tossed in together (less possible, I think).
The catch and release system makes more sense under the older system, where space was a much bigger factor than it is now, but it still feels counter intuitive to create a system where you train a girl's stats to get a benefit from them when they're no longer in your home.