I believe my sister's new boyfriend is showing signs of being a control-freak. What should I do?

I was amy once. It took me a while to see what others saw just because I was blinded by what was suppose to be "love" and not wanting to be alone again. But I was lucky enough to have family that cared about my well being and safety. They showed me how big of a jerk he was from the outside and. Helped me not be stuck on stupid. I advice u to talk to her. Let her know what u are observing but yea it is up to her in the end. At least u will know that u tried and she will see that u truely care about her