The two were spotted leaving a Golden Globes afterparty together on Sunday, January 5 leading one Instagram follower to address the matter by commenting on a post of hers, writing, "Machine gun Kelly Really? I'm out!!! You are now infected."
The 46-year-old retorted by insisting the social media user was wasting their time by discussing her dating life.
"why don't you worry about things that are actually happening and donate to the Australian wild fires rather than waste your time on things that are not happening and never were and also please get a f**king life," she posted.
Another user posted, "U need a man," to which the Brit snapped, "maybe you do since it's so much on your mind xx."
Beckinsale's reported romance with the "Glass House" rapper raised eyebrows because he is a friend of her ex, Pete Davidson.