Echo dot picks up another doorbell notifications

My Echo sends me alerts for when someone rings the doorbell at my mum's house! She also get the alerts for my house. How do I disconnect the two accounts?! The cam's are set up on different email addresses (I can't see her cam), it's just the Echo that tells me. The only link I can think of is that she has me on her prime but I have a separate Amazon account. Any ideas? Thank you!