If she is this:
"The reason I'm concerned about her is that she is one of those influential/flirty types. She'll lead everyone on just to get her way, and since she's in mostly a male field, she has every guy drooling after her."
then you cannot just tell her to fuk off...
these are the best clients.
Tell her if she feels that you overcharged her...then to tell you what she thinks is fair.
Do the work for her even if its for free....
then tell her you will continue a certain amount of work for free if she sends you clients...
yes these flirty types can make guys to anything....
watch your business grow due to her sweet talking all those guys to sign up with you so she can get the free services....
Good Luck.
work with her...