TL;DR - Is there anything that can be done to decrease the likelihood of a GF cheating? Or is she just going to do it regardless of what I do to attempt to prevent it? I suspect my GF is going to cheat on me soon. Are there any good links to good dread game if that's my only option?

I'm looking for some TRP knowledge on my current situation.

I've been dating this girl for almost a year. She told me early on that she has been wanting to experiment with women for a while. So I told her she is free to do it as long as she lets me know when it happens / when it's happening. The way I look at it, I can benefit from this as I can get a threesome out of the deal or potentially have plates and a GF.

Fast forward a few months and she ends up fooling around with one of her close friends and has a great time. She now discovers that all of her curiosities about women have been true and she officially declares herself bisexual. She wants to explore other women and (as I suspected) is willing to have a threesome. - Cool, I can benefit from this.

After she experimented with her friend I got her to agree that it's only fair that I get to explore other women as well. She's jealous about this situation, but is in agreement. - Good, things are working according to plan. So now I can start looking for a plate without feeling guilty.

I haven't had sex with anyone else yet (to be frank, my GF give me plenty and I've taught her how to suck dick like a champ) but I have another girl lined up for later this week I might explore (we'll see - I'm a busy guy).

My GF's only been in about 3 LTR's but has cheated on every boyfriend she's ever had (A red flag I've known about since the beginning). She has this strange complex of "being a people pleaser." She goes out of her way to try and be the perfect daughter, essentially being a little house slave for her mother - Cinderella style. She goes out of her way to please me (described below). And she feels horribly guilty when she's in a situation where she has to reject someone or tell them no (which I kind of think is hamsterring for slutty behavior).
She's described her ex's to me and they are all your typical beta providers. Needless to say, I'm quite different from what she's used to and I'm not the least bit surprised she's cheated on them.

So I told her that she's free to have sex with other women as long as I'm made aware, and if another guy comes along that she really wants to sleep with we can talk about it. I haven't given her permission but told her it's something we could discuss.
The way I see it, if she's aware that I'm going to dump her for fucking another guy, she'll likely just lie about it an I'll never know. I'd rather make her think she can cheat on me and it's fine as long as she tells me, when in reality she's getting a hard Next.

Next month she's going on a 2 week multi-family vacation (which I'm invited to attend but can only spend a couple days due to work) and a guy she blew in the past is going to be there (a guy she cheated on her ex with and has always been curious about whether or not something could legitimately workout between them).

I'm 90% certain she's going to cheat on me in which case I will promptly get rid of her. I can't benefit from her messing around with guys (I can however likely get a disease - YAY!).

I'm currently running some dread game on her but I don't know if this will be enough. Is there anything I can do to decrease the likelihood of her getting with this guy?
I really don't want to Next her, but will without hesitation.

She's told me countless times that she loves me and I have yet to reciprocate the words. Unfortunately, she is pretty much the ideal GF aside from her past and likely future. Since we've been together she has done nothing wrong. This vacation coming up would be the first strike against her - and the last.

She's very submissive, cooks extremely well, cleans my apartment regularly, is the first girl to get me to cum from a blow job on a regular basis - actively trying to learn how to deep throat, slowly but surely experimenting with anal, smoking hot body (5'4, 32 DD's and about 108lbs), cute face, high sex drive, wants to have a threesome with another girl, has an IUD so no babies, fairly wealthy family and she is not the least bit spoiled, extremely intelligent, goes out of her way to give me little gifts or surprise me with food. Will suck my dick without expecting anything in return simply because it turns her on. She's honestly the best girl I've ever dated and I've had my fair share women. She treats me like a king.

However, I think due to this strange complex of "being a people pleaser" and feeling guilty about telling people "no" that this guy is going to make moves on her while she's drunk (and she is definitely a lightweight) and she'll likely not have the courage to say no, nor want to because she's always been curious as to whether or not they "have something" and by fucking him, she'll accomplish a goal from her past as she's always wanted to explore his body.

I know this was long but was hoping TRP could give me some advice other than Next her because that's already the plan if she ends up cheating.