Hmmm... I would say that Laura's problem compared to Tara / Ashley might also be because she's in the "middle"?
I like watching Laura's exploring MC's kink, taking her time to get used to it. As I said in the past, this is part of character development. While girls that go from "nice, faithful, loving girlfriend" to "I'M IN LOVE WITH BULLS' DICKS! PLEASE IMPREGNATE ME!" in less than 10mins are pretty common in H-games, they're also a bit boring due to the lack of development.
But, concerning character development, Tara has an advantage in that. From the start, we saw her disliking Ashley's erotic nature / hunts for men. Meanwhile, in Laura's case, we didn't see much of her past self... By that, I mean we do have some elements, sure, but those are just her / MC having discussions concerning their past, not something that is currently happening. Hence Laura's corruption can seem to be a bit less impactful than Tara's.
As for Ashley, she's pretty much the most perverted character, the apex. Well, at least for now. The student(s) is / are bound to overtake the master at some point. For ex., if Laura gets impregnated by a bull, I think even Ashley would be quite surprised by how far MC / Laura decided to go... would be interesting to see Tara also getting pregnant due to fucking MC while they were both spying on Laura... Imagine her learning the news:
L: "Can't go to the bar"
A: "Why?"
L: "I'm pregnant"
A: "Oh congratulation"
L "<name of the bull> is the father by the way"
A "What...?"
T: "Same thing. Can't go."
A: "What?"
T: "MC is the father by the way"