Diddy's Defense Team Rips Into Bryana Bongolan's Testimony

Diddy's defense team came to life during their cross-examination of Bryana Bongolan ... with one of his attorneys straight-up asking if she's even telling the truth on the stand.

The fashion designer started testifying Wednesday morning and continued into the late afternoon ... and, during cross, Westmoreland asked questions about the alleged incident where Bryana claims Diddy threw a knife at Cassie and she threw it back.

Westmoreland asked Bongolan what started this incident, and Bryana says she doesn't know.

Nicole fired back by asking if she's even telling the truth about it -- a question the prosecution objected to immediately. Judge Arun Subramanian sustained the objection.

Westmoreland then asked if she remembered telling the prosecution that Diddy and Cassie had gotten into multiple knife fights ... and, Bryana admitted she doesn't recall saying that either.

Bryana ultimately says she stands by what she testified to today -- that she was staying with Cassie, and Diddy woke them up, charged into the house and allegedly chucked a knife at her. She says Cassie threw the knife back.

Bongolan testified to using drugs with and purchasing drugs for Cassie and Diddy over the years ... saying she provided Cassie with drugs like OxyContin.

She also testified about an incident where she says Diddy dangled her off a balcony when she was either smoking or about to smoke a blunt with him ... claiming he yelled "You know what the f*** you did!" while her feet dangled.

Ultimately, she says he pulled her back up ... slamming her into the balcony furniture as he did. She says the impact gave her a huge bruise on her leg and caused her neck pain.

Bongolan openly admitted to having a drug problem during her time in Diddy and Cassie's orbit ... and, it seems the defense is digging into that -- and her memory of these times, too.