Maybe to you and others, but I don't care for her. She's only there to add another "crazy" woman that the MC can have sex with just so there is an actual sex scene in the update. Just like Vanessa in chapter 2.
It fits with the character of the MC, though, to have such encounters, particularly when he isn't yet pursuing the girls. He was a bit of a horndog, so to exclude any other pursuits once the girls arrive would be out of character - part of a VN is character building, otherwise you just have a one-dimensional incest machine. Since the VN is also an "A"VN, you have to have characters to have lewd scenes with because you aren't going to have this guy jump straight into bed with his daughters within only a matter of a few days. Something like that, realistically, would have to develop over months.
If this VN were being updated on a reasonable basis (not that it will ever get updated again), the only full-sex scenes I'd expect are with old girlfriends, new hookups, and the like, for several chapters with a slower build to the daughters - post episode 7 or 8 at earliest, with incremental things happening before hand (as we've already seen with two of the girls).
Maybe you want to jump straight to the taboo, but that's an unreasonable thing in this type of scenario. If you want that, go find one of Doc5252's VNs.