So this person DA'ed 2 years ago? And has been coming to the meetings ever since? Or only started attending again recently?
DA'ing for apostacy has got to be a longer penalty. As far as DF'ing goes, it does vary. The elders at my second hall (where I spent most of my JW years) were real stern types. Expect at least 2 years to be re-instated. And in that time, you'd better not mess up. Come to every meeting, no matter what the weather. And hope an elder doesn't have anything personal against you. In my early 20's I dated a girl from another state. In her congregation, she said DF'ed people were usually re-instated in about 6 months.
But DA for apostacy? Why go back?
My thought would be if she really did investigate the JWs, she couldn't go back. She could pretend, and try. Maybe she misses people. Maybe she felt a part of something. But the longer she sits there, hearing things she knows are wrong, I think it's less and less likely she'll go through with it. In the meantime, she can find what she liked about the JWs elsewhere. It doesn't have to come from a church either. If she goes back, knowing what she knows, she's not being true to herself and wont be happy (unless her plan is to stir things up )
I'd suspect the elders would be very cautious. Religion is all about your beliefs. Cults have to have make sure your beliefs are acceptable in every way. Her mind was at one time "tainted", which makes her very dangerous. In ways that are very subtle, she could taint others - even without knowing it. There are all sorts of dangers with her. Maybe she's out with a small group in service. One of the others might be curious. What was it that made you think this was all wrong? Then it spreads. Maybe it's certain things she wont do. I've seen JWs who don't push 1914 because they have serious doubts about it.
The best outcome is for a long, drawn-out process that makes her get tired of it or fed up with what she's hearing and she quits.