If you have such short hair that there is no doubt of its all going underwater, then you do not technically require a mikveh attendant. A woman with longer hair could be permitted to immerse on her own were she to put her hair in a loose net.
However, to avoid problems, the practice in many communities is not to distinguish between women but to have an attendant wait on everyone.
Please note as well that a 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).