Christine Quinns COVID Claims are BS!!!

"Selling Sunset" star Mary Fitzgerald has had it with co-star Christine Quinns lies and drama, and her COVID cry is the nail in the coffin.

We got Mary outside The Oppenheim Group office Wednesday ... and shes convinced Christines recent COVID reveal -- which she says caused her to miss the reunion show -- is just a shady way to back out last-minute and avoid facing her fellow castmates.

Mary says the cast tested twice before the Sunday taping ... and according to Mary, Christine came back negative both times. Mind you, the last test was on Friday, but Christine says the next day she tested positive.

While Christine is undeniably an important character on the show, Mary admits it hasnt been pleasant to work with her in the office.

We also got Christines boss, Jason Oppenheim, outside the office, but mums the word on his thoughts about the COVID drama.

He wants everyone to be a team player and show up for filming, but he gets the other side of the coin -- Christines been going through a lot with almost every cast member ganging up on her.

As we reported, Christine was on a film set 3 days after the reunion taping ... after her rep told us about Saturdays positive test. The CDC recommends 5 days of quarantine after a positive COVID test.