DJ Boof, longtime disc jockey for "The Wendy Williams Show," says folks in the studio didn't understand the extent of Wendy's illness... and he thinks her family members are the only ones who can help her.

Wendy's former TV colleague joined us Monday on "TMZ Live," and he told us it's been sad to see his friend going down the road of cognitive decline.

DJ Boof says people on 'Wendy' knew something was going on with her, but they didn't realize just how sick she truly was ... namely, issues with alcohol abuse, and eventually, being diagnosed with aphasia and dementia like Bruce Willis.

A new Lifetime documentary, "Where is Wendy Williams?" highlights her struggles with excessive drinking and some of her outbursts against people on the show ... and DJ Boof tells us he knew Wendy needed help long before the program aired.

There's some question about who is best equipped to help Wendy ... her family, her inner circle or the woman who's Wendy's legal guardian -- and there's now a heated conflict between those factions.

Boof says he's kept in touch with Wendy since her show was canceled in 2022, and she vanished from the public eye ... telling us when he last saw her in Miami she seemed to be doing great.

Wendy's family is down in Florida, including her sister and her son ... and DJ Boof tells us why he thinks that's the best place for her moving forward.