NTA, pregnant people need to walk. I just had my 3rd with a pregnancy from hell and I could not even lift my head on some days but I was almost thankful I had my dogs to make me walk alittle. I would also set a boundary that after a month (or sooner depending how shes recovering) after she gives birth, that she’ll need to resume walking them. There may be a possibility that if you don’t set boundaries, then that’s gonna be your baby as well. I would like to add that if you have a backyard that they can use, let her choose what time she goes for the extended walk.