Hi and congratulations on your pg!

I don't know you DF but if she is anything like me then the mere feeling of being pressured to DTD when I'm not up for it turns me off like a tap. I
Yep, I have to agree wholeheartedly with that. And further to that, anything that even might turn into DTD can feel like pressure ie. your suggestion of having a shower together. Which, by the way, is lovely but if your DF is somewhat "allergic" (not literally of course, YKWIM) to DTD at the moment in her mind she'll be racing 10 steps ahead. For example," a shower means being naked. In a small space. There'll be touching. Naked touching. And at least some kissing. He's sure to get aroused. And then he'll want to DTD and I'll have to say no!" So for her the easiest way might be to just avoid all situations where she has to decline/put a stop to anything intimate.

See, your DF knows that you want to DTD. She's not oblivious. And she also knows that she doesn't want to. So it's on her mind more than you might think. And it's also probably making her feel worse than you might think. I'm sure that she feels bad sometimes (maybe every time) she says no.

As the other posters have said, it can really be as simple as she just doesn't feel like it. At all. Hormones have funny effects on us! I've had similar experiences (never been pg, just out-of-whack hormones) and the best thing for me was to talk to my DP about it all. Now, if he had said "why don't you want to DTD?!" I probably would have gotten upset and defensive. But as it was, he came to me and said "this is how I'm feeling and I don't want you to feel bad, I just want us to talk about it".

Sorry for the ramble! HTH

PS: personally, I don't think it's such a good idea to bring it up with the MW without having talked to your DF first; she (DF) is no doubt sensitive about it anyway and might feel embarrassed/ambushed/angry if it comes up as a surprise topic with the MW.