Yeah it's avoidable if I avoid any sexual interaction with the new girls, so if I avoid them sure I can avoid the lesbian sex but I lose two LI because there is no choice at all for them to not be into each other, to not interact sexually between each other, like there was with Tasha.
The new girls were lesbians that now are bisexual but since they were together before being with the MC, their focus won't be the MC, but each other and then the rest. The only way to avoid the lesbian sex scenes is to avoid them completly, because they were bonded before the MC showed up, so any future group sex scene with any of them and other girls will include lesbian sex because that's what they are into.
So right now there is no way to avoid the lesbian sex if you want them to be LI, the only way it's to avoid them completly, but you still will see them often because they are important to the plot, so either a forced kink or lose two LI, if this will be the last time a choice like this happens I could try the game again later losing two LI but if it will be the norm from now on then I guess I will stop here. Because right now it's character desing that they are lesbians, but maybe the next one would be an intentional choice that she is a dom and if you want her you must be a sub, or maybe another LI would be into cucking you or something, or into group sex with other guys, that's the thing with forced kinks once you force one there's no telling what will be forced next.