The way to save this relationship is not for her to start policing his social media, it's for him to admit he's been cheating. (He is cheating. If he was being hacked, he wouldn't want to hide the fact that he's improving his data security, he'd show it off.)
Then, if they both want stay in the relationship anyway, they can have the discussion about how they're going to deal with his cheating. Which may involve him agreeing to her monitoring him, or may not.
The other option is for her to decide she can live with him lying, constantly, about important things, which means a) separate finances and b) regular STD checks or condoms in the marriage bed and c) not actually trusting him with anything else important. Some women are willing to make this compromise. Trying to control his communications does not help with it.
Or, she can do that while either waiting for him to come clean or deciding if she wants to leave. But she needs to take practical steps to deal with the fact that the father of her children is untrustworthy either way.
no subject
Then, if they both want stay in the relationship anyway, they can have the discussion about how they're going to deal with his cheating. Which may involve him agreeing to her monitoring him, or may not.
The other option is for her to decide she can live with him lying, constantly, about important things, which means a) separate finances and b) regular STD checks or condoms in the marriage bed and c) not actually trusting him with anything else important. Some women are willing to make this compromise. Trying to control his communications does not help with it.
Or, she can do that while either waiting for him to come clean or deciding if she wants to leave. But she needs to take practical steps to deal with the fact that the father of her children is untrustworthy either way.