Heather McDonald Dishes On Her Hangout Session with Britney Spears

Heather McDonald's spilling all the deets about her hangout sesh with none other than Britney Spears, who shared -- then swiftly deleted -- an IG clip of their night out.

The clip made it seem like Heather and Britney were lifelong besties, with the pop star screaming in joy while Heather nailed a Drew Barrymore impression -- but HM explained on "Juicy Scoop with Heather McDonald" they had actually met only moments earlier!

It all went down back in December as Heather was dining out in Hollywood, where she spotted Britney celebrating her birthday with her manager Cade Hudson.

Since she'd met Cade before, when he called her over, she jumped at the opportunity to swing by and tell Britney she enjoyed her book.

Heather didn't want to be all up in Brit's biz, so she returned to her company -- but Cade called her back 'cause turns out Britney actually wanted to chat some more.

Cade then decided to stir up some fun by telling Britney how great Heather was at impressions, and urged her to do one of Drew -- which you can see in the clip recorded by Britney, who broke the venue's strict no-filming rule to get the footage.

Heather even busted out an impression of Britney spinning around and dancing, just like in her iconic IG clips -- and Britney totally took it like a champ.