Monogamy vs. Exploring a crush: Seeking perspective on boundaries and trust.

I don’t know if this is the right community but I need help. I 25/NB have been with my partner 26/F for 5 years. I am autistic/demisexual and choose monogamy. My partner loves me and wants our exclusive relationship; she is certain she wants a monogamous life long-term, but she is currently unsure if she can be fully monogamous right now. She is interested in ENM. She developed a crush on a coworker ("X"), who is poly/ENM/RA. X is part of her social world, and my partner wants to explore what this tension means without "lying" about her feelings.

The Incidents:

Weekendtrip: X invited my partner on an exclusive weekend trip. My partner asked how I’d feel if she went; I said I wouldn't feel comfortable. My partner was disappointed by this boundary.

The Van: During a work stay, we agreed on "no 1:1 sleeping situations" with X. It happened anyway, and I was informed after the fact. The next day, X asked for another exclusive night. My partner asked me for permission 2–3 times after I had already stated I was uncomfortable with this.

The Meeting: To rebuild trust, I set a "no 1:1 private meetings" boundary until our relationship feels secure again. A group meeting (3 people) was planned; I agreed. My partner later confessed they were actually alone, justifying it by saying the meeting felt "neutral/just friends."

The Conflict: My partner shares "transparent" thoughts, like considering staying late at work specifically to catch the same bus as X. When I ask for distance (since we are at a breaking point), she often feels controlled or that I am overreacting to "small things." She seeks exact definitions of what "private contact" is allowed.

Questions:

How can a partner "explore" a crush/tension while maintaining the security of a monogamous relationship?

At what point does actively seeking 1:1 time with a crush cross the line into emotional infidelity?

Is "zero private contact" (outside of essential work) a valid boundary to heal trust, or is it too restrictive given they work together?

How do I stay firm with my boundaries without becoming controlling or suppressing her need to figure herself out?