How to deal "kindly" with a nervous nellie dog parent?

The best thing to do is to let her know in advance of the possibility you might be late. She'll worry more if you are late and she is in the dark. I've had owners who constantly ask how their dog is doing and don't wait for my regular updates. You just have to deal with them professionally, give them more information and status than anybody really needs, and eventually they will come to trust you with their precious pups. I never mind and am usually more annoyed with the owners who never ask or never respond to my reports.

If the texting doesn't taper off in awhile, then you might mention that you do have other clients and, while you are happy to provide updates on a daily basis, you might not be able to respond to all of her texts. Assure her that, if there is ever any kind of situation she needs to be aware of, you will contact her immediately.

Keeping her informed that you may be a little late for dinner, is best. If she's waiting to see when you were there, it may make her more nervous when you don't show up for 30 minutes.

When you're done with each visit, send her good pictures of her dogs happy and cared for. Give a brief update of how the visit went: dogs were fed and ate well, everyone went potty and poop outside, cleaned up a mess in the hall, left everyone free-roaming/crated, made sure the doors were locked, etc.

All you can do is give a little extra care with updates and stay professional. Some people need a little more time to trust.