If they signed a lease giving them possession April 15th & have given first & last month's rent, (first month due on the day the lease begins & last month when they sign the lease), that's when they get the keys. If a unit is vacant & ready some landlords will let you move in a bit early. Some charge you prorated rent for that period, others don't bother. In any case, they're responsible for rent on that unit as of the 15th - period.
I'm surprised she has all this time to stuff & puff. The week before a move is usually a PITA - making sure address changes went in, shifting any utilities you're responsible for, confirming any expected deliveries & all of that. Right now with most business being conducted by phone or online, it can take hours to get through to a warm body to deal with your issue.
I'm getting the impression she's leaving the furniture behind with Bibi? Awfully generous of her, unless of course, he bought it all; I simply do not know either way. That should make her packing a lot easier if she's just bringing her clothes & personal possessions. The longest part of doing that would be going through cupboards, closets, etc. to make sure she doesn't forget anything.
Over the next several days, I can see her amplifying the work involved with that into a right old mountain & triggering even more feeding frenzies. I watched a few minutes of her "infomercial". The woman can barely breathe sitting down & talking. What I wouldn't pay to be sitting in a car across the street on moving day, (within ear shot), just to watch the shit show. I'd probably learn a few new fun combinations of swears...LOL.
Good news, Chantale! Next Wednesday in Ottawa the weather is calling for mostly sunny with a high of 43F. That's about as good as it gets for the Ottawa region this time of year, most years. My point is, lousy weather won't serve as an excuse to put off the move "until the weather's nicer". Bibi must be almost counting the hours by now.