Need advice/help please!

A few years ago my girlfriend did a nude photo shoot with a former colleague of her, it turned out that he was in love with her, but apparently was not mutual.
Recently he contacted her again, and they would would like to do a new shoot! My stomach turned a bit when she was talking about it out of jealousy that another man might see her naked and her "orders" would give .. but I found it quite a horny idea ..
A considerable time nothing was said about it, until a few days ago;

She told me: "It would be the last weekend of May, that I go to him and spend a weekend with him, and they will be brainstorming about their" project. "My first reaction was:" You ask me for a weekend to spend with a guy who has seen you naked already, and on top of that had feelings for you ... no I don't think so. "
She seemed a little upset about my response, but I said a little later her I have nothing against the idea and that I trust her ...

Now I started thinking about it more and more and I started thinking that maybe this could be a first step ... from fantasy, to reality ...?

I do not know whether I am ready to .. fuck I really do not know ..
I have totally nothing against her posing naked for him agian, because I am an artist and since I was 15 I drew and photographed nude models ... I look with an artistic eye to such things ...

Hence this post: I need advice and help on how I would approach this in a good way and not screw this up for me and that she would be angry with me ...
Would I let her go, Would I let her pose nude, its a whole weekend to stay with him, ..? How do I tell her that I think that I think it's a horny tought, without her thinking I'm a dirty and perverted guy ...?

Any advice is welcome, but seriously of course!

Cheers

Kenedus