I want to involve another man in sex and DP my girlfriend but I’m scared of telling her this

First of all, sorry for the long post but I feel like some context is needed here to understand my situation.

Me and my girlfriend have been together for almost 2 years and we have a wonderful romantic and sexual relationship. We’ve been very open with each other sexually right from the get go and this has helped us tremendously. So far, we’ve successfully fulfilled each other’s fantasies and we’ve had a lot of fun with everything. She made me realize that I was into a lot of stuff that I had no idea I found hot and vice versa. With her help, I explored much more things that I wouldn’t normally do (like prostate play, pee play, light bdsm).

At some point we decided to buy some toys to play around with, so we got some dildos, butt plugs and a BDSM kit. We started experimenting with the dildo and that’s when things started to change for me.

The first time we tested it I was eating her out and using the dildo for vaginal penetration. I suddenly became very aroused and in the moment, but I didn’t really realize why. Then, when we tried it again, I had her suck me off while penetatring her with the dildo. That’s when it clicked for me. I loved seeing her pussy get fucked. Afterwards, I started looking into threesome porn (2 males one female) and now, all of a sudden, the idea seemed incredibly hot to me. This happened a couple of months ago and it’s pretty much the only porn genre that I watch anymore. This has never crossed my mind before and I was usually skipping these types of videos.

Since then, I’ve tried to make some moves in this regard and drop some hints. One time when we were having anal sex I used the dildo on her pussy and she loved it. More recently, while sexting, whenever she would send me videos of her using the dildo, I would tell her that I love seeing her pussy getting fucked. During our last sexting session, I told her this again, and then I told her that I would love putting my cock in her ass while another cock fucks her pussy. She said that’s hot and then I told her that I bet she would love having 2 cocks inside of her, at which point she said “can we get 2 of you?” I feel like this was sort of an evasive answer as I’m certain she’s not sure if I’m talking about a literal cock or a dildo (I always say cock instead of dildo while sexting).

I feel like I’m threading on dangerous territory here and I can’t just outright tell her that I want us to involve another man. I’m scared that she won’t be down with this and that this will be a breaking point in the relationships. We’ve talked about threesomes before, but those wore in a MFF context. She said she wouldn’t do that as she’s not the sharing type. I’m totally fine with that, as I can’t say that I’m a big fan of the idea, but we never talked about a MMF scenario.

Not really sure how to proceed here and what other hints I could try dropping, at least to try and see how she feels about this