Without wanting to add up to the fire I can see is already starting to flame, and to further inflamate you (or at least, it seems you are going in that direction), you do realise that the what is the difference between "outgoing and active", and what is a "slut", especially if "outgoing and active" for you means maximising the number of guys she has sex with, is unfortunately mostly a matter of points of view ?
Can be complained that if a woman tries to sleep with as many men as possible she is called slut, if a men tries to sleep with anything that breaths is a "macho role model" (I don't agree with the role model part, and in diffferent countries "macho" is meant differently), something I personally don't agree with, and can be said it is unfair.
But it stays that outgoing is one things (it has no sexual element in itself), active sexual another, trying to sleep with the maximum number of people possible another.
One thing you should remember also, by her background, it is actually "normal" that Myriam has acquired a submissive tendency, so for some time may easily fall in that. And for the same reason, it is not too strange that she may overcompensate once she does not want to fall anymore in that pattern, by trying to be dominant towards others.
Both type of behaviours can happen to people who had what for them was bad experiences (like Anthony and the relation or marriage with him).