need opinion

so, me and a friend of mine work in the same office and i had gone for a business trip for around two weeks, once i came back she told me she has become friend with a guy from work. please mind she is in a happy relation for past 8 years and planning on marrying. so this new office friend lets call him "P" also became my friend but since we did not want any office gossips we avoided being friendly. we have been to a trip etc. last weekend all three of us were spending time in my home and started binge watching. my friend fell asleep, but me and p continued watching. we ended up kissing each other and then whenever got a chance we did. the problem is my friend is very possessive about "p" and he knows about it and i know that too. so we are basically walking on egg shells with her. i feel she doesn't even think that i and he can be close. for her its either them together or us three together never me and him. she gets annoyed if he doesn't pay attention to her for even a minute. he thinks that even if he faces sleeping me and not her and she notices she will get pissed. and i am not understanding, whats going on. i know i am not jealous. i am just confused.