Deliberately sabotage her own party on a regular basis.
Hang on, lets not murky the waters on that point. Whatever else people think of Abbott we've had documented evidence of Labour staff actually deliberately sabotaging the party - i.e. leaks to journalists, delaying investigations and disciplinary procedures, hiding members funds. Abbott wasn't involved in any of that.
To be fair I think you're both kind of right, but not quite sure sabotage is the right word in either case?
As for what Eggo said, I don't think she was sabotaging under Corbyn, as to sabotage something you have to intentionally damage or destroy, but the party wasn't going to and didn't win, and thus was technically already damaged, she probably made little difference either way. Does it matter if you break something which is already not working? She wasn't doing that intentionally either, she was just not up to the standard required. Sure, when the party became electable, it could be sabotage, but it would need to be intentional, and to me it just comes across more as stupid, especially due to her previous.
As for what Stu said, again, I wouldn't really count that as sabotage from your example. It's like if the coach says, "look lads, we're 5-0 down, lets just call it a day eh?", and then criticising some of the other players who go against orders and actually want to try and reverse the result by going in a different direction. Sure it's going against orders, but play to win etc. You have to crack an egg to make an omlette etc.
Sometimes "sabotage" can actually be for the right cause, but of course, there will always be disagreements over what the "right" cause actually is. It's never great going against the leader, but a good leader can control his team, and get them going in the same direction. The leader should quit when he knows it's not working or the team want to go against them.