The singer was performing live in L.A. Saturday night ... and while she was crooning to her smash hit single, 'TiK ToK,' folks noticed a change in the wording -- right from the beginning, too. Of course, that track starts like this ... "Wake up in the mornin' feelin' like P. Diddy."

What Kesha sang at the Hollywood Palladium, though, was different ... she said, "Wake up in the morning' feelin' just like me." In other words, she completely dropped Diddy here.

Interestingly enough, Kesha did the same on her Friday night show in Oakland. The Oakland performance of 'TiK ToK' looks incredibly similar to the L.A. gig -- but we did some digging and as it turns out ... Kesha's stage design/lighting is exactly the same for this song at her shows lately. So, basically -- there's no doubt she changed the lyric twice this weekend.

What makes this stand out even more is the fact that just a few days ago -- before Cassie filed her lawsuit -- Kesha was performing in Denver, which you can see in the YouTube video above ... and there, the Diddy lyric remained.

Long story short ... it seems Kesha is taking a stance on the issue, which is notable considering she has long labeled herself a survivor of alleged sexual assault -- having infamously accused Dr. Luke ... which he vehemently denied and sued her over.

In the end, they settled their legal battle and Kesha said, "Only God knows what happened that night. As I have always said, I cannot recount everything that happened."

That saga was arduous in and of itself ... but seemingly pertinent to the decision Kesha's making here about Diddy. Like we said, he too has outright denied Cassie's allegations -- accusing her of a money shakedown ... this before coming to terms out of court a day later.