Trying to update OS, latest version isn't compatible

Hi everyone. I'm currently using an older OS (10.9.5... I know) on my Macbook Pro, mostly because certain programs would not work if I updated. However, I've decided to upgrade those programs and therefore can update my OS. My issue is that when I go into the app store, the latest OS isn't compatible with this computer (it was purchased in late 2010). My mom has a newer (only by a few months) Macbook Pro and was recently able to update her OS to High Sierra, so I'm wondering if there's any way I'd be able to get that on my computer? The most recent OS I find in my "purchased" tab is Yosemite. I suppose that would be better than nothing, but I'm trying to get the latest version I possibly can for this computer and can't figure out if there's a way to do that.

I don't understand why Apple doesn't just allow you to download the latest compatible version... would make more sense! But any help would be greatly appreciated. Thank you all!