My girlfriend and I have different morals about sex?

It's early, and I highly advise cutting your losses and parting as well as you can.

1) You are Sexually Incompatible with each other. You will always see her in a way that is disgusting, even if she is otherwise a good person.

2) There is a decent chance she will cheat on you because you simply cannot supply her unreasonable needs.

3) Having additional sex participants violates your requirement, and her commitment to an Exclusive Relationship.

4) She violated her her commitment to Exclusivity at the suggestion of bringing in additional sex participants. So technically, she already did cheat on you.

5) You are incompatible in morals and ethics.

I'm not saying she is a bad person. Give her credit for her honesty of being upfront with you early on in the relationship. But you need to split amicably because the pair of you just don't have what it takes to comfortably and physically have an Exclusive relationship.

You've been dating only 3 weeks. You haven't invested that much time with her and aren't that involved romantically.

This girl is not for you---or most guys. What she does with her life is her business, but you don't have to be part of it.

Be smart and break up with her now. YOU are the one who has good morals. She doesn't. I would never trust a girl like her.

Natural.

"I am afraid she will cheat on me"

Yes, she likely will engage in additional sexual-relationships if she experiences any dissatisfaction with you.

I strongly recommend ending this relationship as it is evident that your girlfriend is merely concerned with appeasing her own sexual-desires.

EDIT: "If the threesome is FFM then I would say you lucky lucky bastard."

Johnathan, do not behave so naively. "FFM" merely translates to a male individual exerting excessive effort to please two female individuals sexually.

You two need to have a talk. If th e relationship is going to last you will have to reach an agreement about sex, and fidelity.

She is hardly a Catholic behaving like this with such sinful behaviour.Let her go and fond somebody else.

If the threesome is FFM then I would say you lucky lucky bastard.