Kelly Osbourne
is clearly not a fan of Lady Gaga!

The starlets' feud dates back to 2009, which started when Osbourne attacked Gaga for skipping the Grammys red carpet. Kelly says the singer's "Little Monsters" started sending her death threats after she dissed her.

It looks like Gaga was trying to squash their drama over the weekend though, when she sent Kelly a birthday cake through her mom, Sharon Osbourne.

The "Fashion Police" star was less than amused and posted a series of tweets attacking the "Applause" singer. 

But it didn't stop there -- Kelly blew off some more steam via Twitter mocking the pop star's gesture. 

She also posted a photo of the cake with the hashtags "#EatMyS**t" and "Hypocrisy." In the past, Kelly called Gaga a hypocrite for preaching against bullying, but having fans who bullied her.

It doesn't seem like the E! star is ready to call a truce anytime soon. Do you think Gaga meant well?

Whose side are you on? Vote below and check out some of Gaga's craziest looks in the gallery above!

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