This is a game for adults with adult themes which include slavery, body horror, murder, cruelty, the killing of children and you are upset about some "mild" sex with a horny/manipulative Drow that you have to take a specific evil path to even get to? Ok, that seems totally reasonable.
Minthara and the Drow in general use sex like a weapon, to control and get info and manipulate people, which is exactly what she does. It is an accurate portrayal of their culture.
This comment is golden. I fully agree.
It amuses me that the rant of the original poster got 23 pages of comments (nothing personal, btw). If you don't want to watch it, just skip the scene or don't be involved in romances. This reminds me of a comment made by GRR Martin that he got a lot of complains about sex and none about the violence in his books. I am fine with both as long as you know what you buy. And BG3 is quite clear about it.
And by the way, I do not think that game sex scenes should be 100% realistic. That's not the point of the game, lol.