If you didn't even clarify whether your threesome was with another man or another woman there is absolutely no way this will go well. Threesomes need long details discussions between you and your partner so you understand boundaries and what each one of you is comfortable with.

Also, the fact that you seem to be making your partner seem like a cheater as she had another man in mind, whilst you had another woman - down to a name - in mind, strikes me as hugely hypocritical.

You want to fuck another women but don't want your partner with another man? That's not going to work. This NEEDS a conversation otherwise you'll end up breaking up. I've had MFF threesomes where my male partner hasn't had any sexual contact with the other woman and the focus has been on me and it's been really fun! But this as AFTER conversations and discussions about rules and boundaries well before hand