People are self centered. This can lead to hypocrisy in many ways.
In this case, what's good for the goose, your wife and her bf's deep relationship, spending whole weekends together on a regular basis, is not good for the gander, you doing the same thing. Or wait, is the goose the male and the gander the female?
Anyway, there was another case here of a Christian couple in which the husband had a secret affair with another Christian woman. Then the affair was discovered, the original couple decided to be poly, and the mistress was told she could continue in her relationship with the husband, with the wife's approval. The mistress was appalled and ran away.
Jealousy is usually based on a fear of loss. Your wife knows she loves both her men, and since you aren't jealous, she doesn't fear losing you when she loves her bf. However, she still fears losing you when you love another.
Getting her to see love as expansive and abundant, not scarce, is what needs to be worked on here.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
me: Mags, 59, living with:
miss pixi, 37