Thank you for the answers!
frenziedfemale, clearing the data worked. Thanks! It's strange, though, the Gallery doesn't seem to recognize pictures saved from Google Drive anymore (that is why, I assume, the folder didn't show up after the update - there were only photos from Google Drive there). When I try to save new pictures from Google Drive, they get downloaded and take up space, but they just don't show up/don't get recognized by the Gallery as image files at all.
But at least it works fine with images downloaded from elsewhere, that's good enough.