1. Ask her to show you where the Watchtower has explicitly said this. (Make clear you're not interested in what Elder Know-It-All says. You want to see where "the faithful and discreet slave" has said it.) If she can't produce that, isn't she running ahead of Jehovah's chariot? Isn't it wrong to do that?
2. If she produces some WT publication where this is actually stated, ask her how she will view things if it turns out NOT to be the tribulation after all.