Do you think it's right for me to want to know about my (now ex) girlfriend's sexuality?
Why do you want to know this about your ex?
Because I want to know whether she prefers women or men more
You should not be concerned with an ex. You will be better off if you move on and focus on other things.
She is a slut anyway.
It's understandable that you would want to know about an ex's sexuality, however, it is no longer your place or your business to question these things. It would be best to focus on yourself and move on.