Any surgeon will tell you that any aneasthetic is a risk. However, your mum will be checked by an aneasthetist before she has her op (she may have been already) who will look in detail at all her past medical history.
From what you say I take it she is having a laproscopy which is quite a minor op. As Anchoivies says, medications have much evolved and are quicker acting. They are becoming safer all the time.