Fozzie, who is 4 months old, is very very careful where he steps when my neices come over (one is 9 months and crawling, the other is 2 years old and talking & walking ). You should try keeping Mercedes tethered at first to be sure you can trust her. If you can't, it definitely is better to baby-gate her into a room or crate her for brief periods than risk her accidentally knocking the baby over.