As it stands she's right. Labour haven't proposed anything at all that might change that course of events. For instance they could get wholeheartedly behind a second referendum, but they would need to decide that soon, they would need to be clear about what the question would be, when it would be and so on, and most importantly they would need assurances from the EU as to if and under what conditions they might allow us to remain, as without that Leave would win again anyway. I don't see Labour preparing for any of this or anything else, and time is running out.
This may be so or may not, but unless some one asks the EU Council to meet and decide what the terms would be then we couldn't be sure they wouldn't insist on us joining the Euro, Schengen, and the rest, and if Remain couldn't win the last referendum they sure as hell wouldn't win another with that possibility still open.
I don't know where all these people with brains are hiding, because I'm seeing absolutely nothing that's likely to stop Brexit occurring so far.