I am happy to learn two things: a). Coronary Arteries of your mom do not show any disease b). In your own words "she is very fit". Therefore, problem is a little something which did not go right while doing the procedure. If that is the case she is going to be up and well within short time. I can only hazard a guess about what went wrong- it could be -as actual location of Artery
varies in some- the needle while administrating local anesthetic
could have gone a little deeper or sideways. So, delayed recovery is expected. Your doctor will also investigate for her fall in BP while standing (a separate malady) and hemoglobin
(she could have been anemic possibly). All these illnesses are eminently treatable so worrying is not going to help. One last thing, you have mentioned about her lips going blue after swimming. My concern would was the temperature of water colder than normal that day. Tell your doctor if was not colder tell your doctor if her finger tips and toes also became blue; your physician shall be interested in investigating for the cause. I hope I have answered all your questions. With best wishes.
Dr Anil Grover