Don't do it. In the past, I used to bend my rules but I've noticed that these guests tend to be difficult to please. I would decline and tell them that Airbnb does not allow proxy bookings and Grandma needs to sign up for her own account to book - alone!
I would say something like this:
Hello NAME,
Thank you for choosing my place. I'm so happy you inquired and I'm truly honored that you love my house.
However, I cannot accept this reservation because I do not allow proxy bookings on this listing. If your mother is interested in staying with me, she needs to create her own profile and then request a reservation.
Also, I do not allow children and infants under 12 years old in this listing due to safety concerns. However, there are other great listings in the area that offer such amenities.
Good luck and stay safe. Please let me know if you have more questions or concerns.
Gerald
I also don't allow people to book unless they have ID verification. I think it's now required for all bookings but when I started as a host - it wasn't. Sometimes we cannot let the desire to please and server others or to make extra money get ahead of our sanity and safety. Best of luck and hope everything turns out great for you!