Theirs was a complicated relationship but I think it was very well explored within the movie, I've actually had quite a few conversations with friends about it in the last couple of days.
I had read the book the movie is based on so I knew some of the history between Tatlock and Oppenheimer, but I thought Florence's portrayal of Jean was pretty clear that she was an independent woman who was in a relationship with Oppenheimer but she needed him as a friend (with benefits) more than she wanted him as a partner in a relationship, especially due to her depression - she needed to know he'd answer her call whenever she needed him and he always did ... Until he didn't and then she killed herself.
Oppenheimer was initially more into Jean than she was into him; he proposed multiple times and she turned him down each time because while she loved him she wasn't in love with him, she was on her own academic path and didn't have any intention of giving it all up to become his wife (as was expected of women at the time).
I thought that was eloquently shown by the repeated theme of Oppenheimer bringing her flowers, despite her telling him not to and then each time he brings them she doesn't do the socially acceptable thing and accepting them with grace and getting rid of them later. Instead Jean immediately takes them, tells him she didn't want them, bins them (often while holding eye contact with him) and then moves on - she doesn't hold it against him but she also doesn't change her stance.
Their relationship is one of mutual understanding - she needs him around to be her support and her friend, she doesn't need him to be smart or intelligent or some sort of authority figure like everyone else. The only time she asks him to use his intelligence is so she can get herself off while they're having sex, not because she wants him to be smart but to exert control over the situation.
However, over time as Oppenheimer was taken further and further away from her by his marriage, kids, the Manhattan Project etc she seemed to realise she did need him after all, just as he realised he couldn't be there for her anymore and had to end their relationship. This took the power that she was used to having away from Jean and ultimately (in the movie at least) it is shown to contribute towards her reasoning for committing suicide.
The only other time there is the "gratuitous nudity" is in the trial scene where Kitty having to listen to her husband recount his relationship with Jean and again I think it was used fantastically to show the power balance of their relationship. Kitty and Robert's was a marriage of necessity (which they both never denied) and she did love him but she always knew he was having affairs and she knew that Jean was always "the one that got away" for him and that he felt responsible for her death, which was something she could never compete with, despite her years of loyalty to him.