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.