If you’re so nervous that your cousin may be screwed over, call her rav with your concerns. DON’T take it into your own hands. When I was engaged I didn’t want to hear from anyone other than the shadchan or a rav.
The satan gives his all to destroy everything, especially when something is true. If you heard something and are so concerned for her benefit, ask his Rosh. All you can do on your own is cause damage.