In fact, at the moment I'd be for
more flirty and sex driven companions, as no-one seems to want to sleep with my PC at all any more

Withers has just been asking her why she's all alone.
You make a good point, I've had the exact same conversation. It's very odd, because with Wyll and Gale I've had numerous attempts to start a romance, but Shadowheart and Karlach is completely nothing, and I have a feeling that Act 1 was the only starting point for those romances, which is awful, as those are the only two I was remotely interested in, but didn't really feel that romantic dialogue after killing a couple dozen goblins was appropriate.
On the other hand, the ladies casual clothing being straight out of a vampire night club pushes the balance towards sexualized.