Just want to get some other opinions on this situation.

We have a nanny who watches my 5 month old DD. She's been with us for two months and everything is going well. The nanny seems to be attached to DD and takes a lot of pride in her (showing her picture off to her friends, bringing her little presents, saying how much she missed her over the weekend etc.)

The nanny is very social. A few times a week she walks to the mall near our house where she meets other nannies and they hang out for a while. There is a kids play area and other lounge areas and it's temperature controlled. The walk is about 30 minutes one way (1.4 miles.) DD is obviously too small to play with other kids so she just hangs out in the stroller or on nanny's lap and sometimes naps as well. Since DD is clearly too young to play with the kids, this is obviously more for the nanny's benefit than DD's (so she's not bored just being in the house all day.)

My mom has mentioned on a few occasions that it makes her uncomfortable how often nanny takes DD to the mall, that it's a long walk and must be exhausting for DD and maybe over stimulating. DH and I have discussed this and don't see a problem with it. We feel like DD is being exposed to different situations, people and stimulation which we like. We trust nanny to take care of DD. I've instructed nanny that no one is to touch or hold DD except her and she assures me that no ones does.

Would you have a problem with this? Am I missing a potential issue?

ETA: I would rather them go to the mall than the park at this time of year because it's so hot at the park.