Giordano, it was my advice--my advice having never been a JW. I'm not that old (early 30s) and a single woman so I know the game. The situation being what it is, it was very sound advice: she met him when he was temporarily DF'd (only several months); they date for four months and he's trying to get reinstated. Not to mention, he says he wants to marry her but would only do so in secret. All of this says to me it's very likely he's still indoctrinated.
So they know they're sexually compatible; that's great. But sex can also make you think it's love when it's really just hormones. Been there, done that, have the T-shirt. Because none of us knows the future and because as a non-JW, she is very unfamiliar with the wacky world of JWs, it's best to exercise some caution until she has more information that isn't emotionally charged. If he really cares for her, waiting on the sex while she figures things out won't be a deal breaker. But he may just want to have his cake and eat it too (sex/relationship with a "worldly" girl while getting reinstated into a belief system he believes in). And if he still believes it's the "truth", he might be expecting her to convert or at a minimum live in accordance with it--no holidays or birthday celebrations. No, he may never verbalize it, but it's probably a "given" in his mind. Of course, he'll want his children to live the best way of life.
I obviously don't know the details of every case and I'm glad for every relationship that survives the WT curtain. But I have read some stories here about UBMs who didn't really know what JWs were all about or didn't intervene in a baptism because they thought it was harmless. My first suggestion was to get informed. It wasn't judgment or ill will. If they can live happily ever after with him reinstated and thumbing his nose at WT rules, then that's fantastic. But with the situation as it was presented, that was my advice and I stand by it.