My mother is extremely picky as well, has similar restrictions/taste too lol. Try:
What wrong with Secretary Kim , ( Mom loved this)
Touch your heart
Both are cute office romcoms.
Eulchacha Waikiki ( Very funny, also has one of the cast from healer, younger version of villain in parents friend group the jelly one lol)
Weightlifting Fairy Kim Bok Joo
The First Frost (This is a C- drama, I haven't watched this yet but I read the web novel, it's really good. The reviews are very good for it too.)
Also if you can get her to watch it she might also like:
I hear your voice ( similar to while you were sleeping in supernatural levels, Also same ML, Lee Jong suk),
W
and Chicago typewriter ( W and this one, some of my mother's and my favs, both have some supernatural but I find them not over the top, if that makes sense). My mother really loved these two surprisingly well.
Hope these are useful.