[27/m] My SO [20/f] Has Shown Interest In Hardcore Group Sex. Not Sure How To Handle It... (NSFW I Reckon)

Hey people

So me and my SO have been together for nearly 3 months. I've been around the block, loved and lost, had long relationships so believe me when I tell you that what we have going on is pretty damn good.

We started off casual but fell in love as we went along so the sex has been right out there and open from the offset. She is in to domination with her being domme, with which I had no experience, but I soon liked it. As we became close she decided that she could accept switching and me going dom (not the first guy to dom her but the first guy she had been comfortable with dominating her) and I equally enjoyed it as much as the other way around.

Now bear in mind that I had been stuck with vanilla sex up until now, it's all new and exciting and I love trying these new things. We started watching porn together, and considering her interests I got some "Public Disgrace" videos. Pretty nasty stuff with girls being abused by a room full of people (all in a safe environment with safe words etc of course).

Now here's the clincher: She said something like that would be her biggest fantasy. That's cool.... I guess.... Just not sure I want to see the woman I love and cherish be treated like a cum dumpster by a room full of strangers...

So me being me said that I wasn't comfortable with it but I wouldn't want to deprive her of her fulfilment. We discussed it and she suggested we try both kinds of threesomes and possibly work up to it.

I've never had threesomes or anything and I'm not bi curious or gay so I'm not sure how cool I'd be with a 2 guy threesome, let alone group sex or the decimation of my SO by a group of strangers.

That's pretty much the whole situation, so my problem is: I don't know what to do. I like trying new things but this whole thing is just kinda freaking me out a bit. I know most of the advice I'll get will be "just talk to her and tell her you're not comfortable with it" but I don't want to stop her from fulfilling her fantasies. Has anyone else had a similar problem/situation before?

Also if this is too NSFW for this sub please point me elsewhere.

Thanks!