Reports (eg "In the Plex") have said she reviewed every UI change, above a fairly low bar. For instance, multiple meetings about exactly which shade of blue to use for various controls.

Some people say she brought a valuable discipline and consistency to Google products and held back the worst "designed by engineers" proposals. Other people say she slowed down launches, relied too much on non-scalable personal gut feel, and was arbitrary. I don't know. But if someone previously so central to UI launches leaves, things will at least be different.