There's really nothing one can do to a glass block window to "update" it, short of replacing it entirely. I have two in my home, one of which is in a bathroom and covered with a custom Roman shade when privacy is desired. Some things you just have to let be what they are, and in the case of glass block, the less you try to change it the better, in my opinion. Particularly since a redo isn't in the immediate budget but your friend enjoys the light ... encourage her to accept it as is.

Maybe "update" wasn't the right word. Just looking for options of different ways to treat it. I saw a pic where some of the blocks were painted (stain glass paint) different colors. Someone suggested a window decal but the grid of the grout lines would show through.

Those are the sorts of things that invariably end up looking like Pinterest project fails. Really, where glass block is concerned, leave it alone. Maybe your friend could add a shade or blind to hide the blocks when it's dark out, but that would likely involve custom work so may not be cost effective.

Too, her blocks are so heavily patterned that anything added on top of them, such as a faux stained glass cling, is going to look bizarrely busy.

I would look to regrout the window to make it look nicer. This is a very old pattern of glass blocks - so I would not try to remove them.