I just started dating a couple, but one member of that couple has problems with me spending alone time with our partner

I just got into a poly relationship with a couple who have been together for five years, we've been friends for three, we've all been dating for a month now. They have a whole pattern of existing already. We're all new to polyamory. We all spend time together really well, me and her alone is okay, but she gets jealous when I spend time with him alone. I want to be able to spend time equally with both of them alone without her getting upset. I don't know how to approach the topic since it's all new and I don’t want to hurt her, but I also want to fully enjoy both relationships I have with them separately as well as together. He wants to spend time with me without her being upset as well. Do you have any advice for gently talking boundaries for a new relationship?

We all learned (or, at least, we were all supposed to learn) in kindergarten that it’s generally not okay to do things that make other people feel upset or hurt. So I don’t want to tell you that you’re wrong for caring about this, or that it’s a good idea to just go around doing things that you know make other people - especially people that you care about! - feel upset or hurt.

HOWEVER. As adults in relationships with other adults, it’s not always feasible for your goals to be based on someone else’s feelings. You say that you don’t want her to be upset, but there’s nothing you can do to control her feelings, and sometimes, people are just going to have feelings. You can’t change them and you can’t take responsibility for them. This person chose to enter into a polyamorous relationship with you two, and she is responsible for managing her choices and behaviors in this situation.

My question for you, to start, is how do you know that she “gets jealous” or is “upset?” If there is some behavior of hers that is making this relationship untenable, if she is treating you coldly or picking fights or something, then you can talk to her about that. You can let her know how those behaviors are affecting you, and clarify what needs to change for this three person relationship to function in a way that’s healthy for everyone.

Theoretically, all three of you have the same goal: for him, you, AND her to be comfortable, happy, healthy, and functional within the relationship. You’ll want to ask her what you and he can do to help her feel more secure, and if she asks you for things that are possible and reasonable, try doing those things. Then it will be your turn to let her know how this is affecting you, and what you need from her to make the relationship work.

Ultimately, she needs to manage her own emotions and not make them your responsibility. If she just needs to work through these feelings, then try not to make them your problem or get too fussed over them. Someone can be out in the world being upset without that needing to take up emotional real estate in your head. Figure out whether you and your new partner can navigate your togetherness without constantly worrying about what she might be thinking, and then if there is an issue, address her actions rather than the feelings you’re perceiving her to have.