Bathroom, peeled wallpaper, need to texture n paint

Help:

My step mother is 70 and on good happy pills and painkillers. She got it in her head that she wanted to peal off the wallpaper in her bathroom and paint the plaster walls lastnight, The wallpaper was the only thing she didnt like everything alse is fine and in good shape. She unplugged the fartfan, cranked up the hotwater in the shower and steamed up the room good then peeled off the 70's? foil type wallpaper. I'm not versed in wallpaper at all but what is left is a layer of paper backing and glue, we tried a steamer and remover in another spot and all it does is ball up the fiber of the paper. Luckily the ceiling is smooth plaster.

I did a google search and searched here and what I saw said to use oil based primer to seel the paper and then shoot texture......My question is are they talking about a conversion primer like zinser123 or are we talking real oil base primer?

Im a little confused ,I know water based materials do not adhere to oil bases, Ive wiped enuff paint and mud off oil based trim and cabinents to know its not good adheasion so am I missing something?

Idealy my plan now is to mix a little silica in zinzer123 and roll the walls.....let set a few days (address any bubles) Then shoot knockdown texture , prime, then paint.

Any suggestions?