Andy Cohen just responded to Brandi's claim about the video she says he sent her -- and he now says she's blowing it out of proportion.

He writes, "The video shows Kate Chastain and I very clearly joking to Brandi. It was absolutely meant in jest, and Brandi’s response clearly communicated she was in on the joke.  That said, it was totally inappropriate and I apologize."

Brandi Glanville is putting Bravo's parent company and others on notice that she's prepared to take them to court over this whole 'Girls Trip' drama she's been roped into ... and lays out her grievances in no uncertain terms in a letter that her attorneys just fired off.

The 'Real Housewives' star has lawyered up with the likes of Mark Geragos and Bryan Freedman -- big shot lawyers in Hollywood -- and they sent NBCUniversal a demand letter Thursday that threatens a lawsuit on behalf of their client ... and they're telling the network to preserve all potential evidence as Brandi prepares for what could be a messy legal battle.

The letter, obtained by TMZ, spells out exactly why Brandi is considering suing here -- and according to her legal team ... she feels like she's been chewed up and spit out by Bravo and all other parties involved in producing and airing a show that makes them millions.

They're strong, writing ... "Over the past year, Ms. Glanville has been subjected to a vicious media campaign based on false allegations of sexual misconduct. The false narrative, which NBC and Shed Media have apparently decided to foment, arises from Ms. Glanville’s experience on 'Ultimate Girls Trip: Morocco.'"

Her attorneys add ... "While the experience has been a nightmare for Ms. Glanville, it is far from the first time Ms. Glanville has been used and abused by NBC, Bravo, Warner Bros., and Shed Media. Indeed, Ms. Glanville has long been taken advantage of by the institutions with which she is indelibly tied personally, professionally, financially, and in the public mind."

Brandi's lawyers claim that while she's been loyal to NBCU over the years ... she's only received mistreatment in return -- including this latest saga with fellow 'Housewife' Caroline Manzo, who recently sued Bravo claiming she was the victim of sexual misconduct from Brandi during the filming of 'Girls Trip: Morocco,' but BG defends herself here.

Long story short ... Brandi's attorneys say that Caroline's narrative of being forcibly kissed and groped by Brandi during the filming of that show was actually consensual -- with Brandi's team claiming Caroline was inviting that sort of behavior, which she also alleges was facilitated and even encouraged by producers during the filming.

There's another salacious allegation that Brandi's attorneys float in this letter they sent -- evidence for which is not attached in their correspondence -- that invokes the name of Andy Cohen.

Brandi's team claims that in 2022, Andy subjected Brandi to sexual harassment by sending her a video -- one in which she claims he boasted of his intent to sleep with another Bravo star that night ... and allegedly inviting her to watch it all via Facetime.

Her attorneys characterize her role in all this one of a "sacrificial lamb," and they say Brandi isn't going to take it anymore ... so she's telling Bravo and co. to get ready to go to battle.

She hasn't sued just yet ... but it sounds like she's ready to go to war if they can't resolve things outside of court. We've reached out to NBCU for comment ... so far, no word back.