I believe at the very least that she and Malan were at least dating several years ago. There are pictures of them going back six years or whatever, he has gone on family trips with her family where they were clearly interacting with him and he was clearly there as Jabba's long term boyfriend and was treated as such.
There are posts/comments on Facebook where Jabba's mom is talking about or to him. James talks about him as being her boyfriend. She's not smart enough to trick a dozen people into believing they were dating for what, seven years now, through family outings and holidays and all.
Granted, they haven't done any of that stuff for at least a year now. So it's possibly they've broken up or, most likely IMO, are just staying together out of convenience and laziness. Neither are them are likely to find someone else easily, they're used to their situation, etc.
It's clear there's no love or closeness there anymore, but saying she's been successfully pretending to be dating him for seven years and him going along with it is giving her too much credit.