Anything with like, hauntings/paranormal stuff. I started a playthrough of Resident Evil VII yesterday and she seemed to like watching that, too.
All of that helps a great deal!
Sadly, gratuity is kind of the name of the game if you're talking about slasher movies (which arguably Evil Dead 1 is), and generally a lot of horror movies from the 70/80s onwards up to now. Even the first Halloween is guilty of that for a scene, for how tame it is in terms of gore. Slashers as a genre really don't seem to fit your criteria much anyway, since it's 40 minutes of faffing about before A Guy in a Mask™ starts chain-killing.
(I swear I love slasher movies. I just don't sound like it.)
One classic I can recommend that has amazing creature effects is The Thing (1982). The plot is pretty straightforward ("there's an alien, but where?"), I can't praise the FX enough, and it's light on the
other kind of adult stuff. It had a prequel of sorts in 2010, but I haven't seen it yet, so I can't vouch for it in any way.
Creature features is an avenue you could pursue more generally. Things like The Blob, the Jaws series (diminishing returns on quality I've heard), maybe going into kaiju movies; Cloverfield might even be a good introduction to found-footage after that, depending on if you appreciate that way of film-making.
I do recommend
doesthedogdie.com if you don't mind spoilers for yourself, although you may already know about it (and then, to anyone reading). Very straight-forward way to vet media against all kinds of possibly troublesome content.