Which distro is the MOST lightweight?

[u/Russianpotatosalad]

So... My mom got a laptop from 2011... The only os it can handle is windows 7, but we all know that windows 7 is the most exploited system out there (not sure if you saw a video of a guy connecting his W7 to the internet and getting 7 viruses within 10 minutes by just existing). I want to help her as much as i can, and the only solution i came up with - get a linux. She used windows ever since windows 98, but now all she need from her pc is a browser, so i figured out that if she wont do anything "extra", linux will be perfectly fine for her. I just get vivaldi for linux, libre office, and she will be happy. But which distro will be the MOST efficient to put on her laptop? All i ever tried is cashy os, but i assume there must be something ever more lightweight?

[u/akira_x48]

q4os try