GM Daniel Naroditsky had an article years ago where environment can impact chess performance a lot. He showed a great bullet game of his and then a much lesser quality bullet game of his. He said one was in a quiet library and one was in a loud place (cafeteria if I recall).
That being said, bullet naturally fluctuates a ton and your sister may not be all to blame. Worth mentioning that in your above screenshot, the average opponent rating was 2193.5, whereas in the second screenshot with you losing, your average opponent rating was 2484.14, so that's roughly a 290 average point difference!
Before she started loudly speaking:
After she started loudly speaking: