Alyssa Milano isn't sugarcoating her ties with Shannen Doherty ... acknowledging they had a complex relationship -- but, making it clear the world's worse off without her.

The actress spoke with Page Six Sunday just hours after Shannen passed away following a fierce cancer battle ... admitting to the outlet her relationship with the late actress wasn't always easy.

Milano says, "It’s no secret that Shannen and I had a complicated relationship, but at its core was someone I deeply respected and was in awe of. She was a talented actress, beloved by many, and the world is less without her. My condolences to all who loved her"

If you don't know ... Alyssa and Shannen starred on the show "Charmed" together from 1998 to 2001 when Doherty's character was killed off -- a move she accused Milano of orchestrating on an episode of her podcast last year.

The way Shannen told it ... Alyssa went to producers and threatened to sue the show for a hostile work environment unless they fired Shannen -- so, they did.

Milano dodged the question when asked about the rumor back in February ... and, Shannen tearfully reiterated her claims at a panel just days later -- so, the two weren't exactly buddy-buddy leading up to SD's passing.

Shannen passed away Saturday surrounded by loved ones her rep Leslie Sloane told us ... saying she'd finally succumbed to cancer after fighting the disease for years.

She was 53.

RIP