Please help me understand if there is anything I can do.

-Separated 6 months. -She’s been “dating” this dude for 3 -Brings him around our 4yo son. -he calls him “baby boy” -she sends him photos of the baby monitor.

It’s like they think this is their child? Personally I feel she is falling victim to him taking advantage of her vulnerability during this time, and she is gobbling it and other things up