The Mikveh Attendant
Halacha requires that mikveh immersion be witnessed by a Jewish woman over the age of twelve to ensure that all hair is submerged. This is the primary function of the "mikveh lady" or "balanit."
The mikveh attendant has several secondary roles. Her presence is a good safety measure against accidental drowning. She may also offer to check the hands, feet, and back for chatzitzot (barriers), and may quickly review the stages of preparation to ensure that nothing was forgotten. However, each woman is ultimately responsible for her own preparation and inspection (chafifah and iyun).
If no one is available to supervise immersion, a rabbi should be consulted for alternative solutions. A woman who is particularly embarrassed to be seen naked, even by another woman, should also consult a rabbi or a yoetzet to discuss how to use the mikveh in a way that will make her most comfortable.