We've got two baby gates that DD1 hasn't figured out yet. One is from Bunnings and the other from Toys R Us. Both you have to lift the gate to open it, something a toddler couldn't possibly do.

We have a gate across the kitchen and one on DD2's room. When she was little, I'd put her bassinet in one of those rooms if she needed time out and was asleep or I'd put the swing or rocker in a safe zone, lol. Our bedroom has double doors which we put a plastic kiddies lock looped across the two door handles when required. You can get great covers for round door knobs too.

Our play pen is about 1 x 1m so not big at all. We haven't actually used it yet but it would be a good option if you've got enough room.

The suggestions for her own baby are great too.

Good luck! Hopefully the novelty will wear off soon, especially when she realises how much newborns cry! Lol