Teyana Taylor is convinced Iman Shumpert‘s relationship with a woman is negatively impacting their children — so much so, she wants an expert to get involved in their divorce … TMZ has learned.

In new court documents, obtained by TMZ, Teyana asks the court to let her call on a child psychologist to testify about something she says went down a couple weeks ago, when their daughters — 8-year-old Junie and 3-year-old Rue — were staying with their father.

According to the docs, the ex-NBA star had a female friend and her daughter staying at his home during his parenting weekend with Junie and Rue. Teyana says she knows this because she saw the woman’s daughter and heard the woman during a FaceTime check-in with Junie and Rue.

She also claims the woman was at SkyZone later with Iman and the kids.

Teyana says her oldest daughter was confused after seeing Iman and his companion sharing a bed — and claims Iman told her the “friend” was staying with him because her home was “broken.”

In the docs, Teyana says she feels Iman doesn’t need to be flaunting the fling during his brief time with his daughters — she points out he only has Junie and Rue on the first and third weekend of every month, plus a handful of Fridays.

Still, she believes Iman isn’t aware of how his actions are affecting the children — which is why she wants a child psychologist to weigh in on the subject for the judge in their divorce case.

New boos aside … Teyana additionally wants a financial expert to testify, because she alleges Iman’s withdrawn nearly $4 million from several shared accounts