You can't banned your sister from dating even if it is to protect her from the dangers of it. It is her own life after all, and teenagers are notorious for resisting and rebelling hard against any rules that they might deem unfair to them. Instead, I agree that you could talk to her and tell her your concerns while letting her know about the dangers and how she can protect herself from those dangers.
A great way to do it is to educate your sister on taking care of her welfare and never putting herself in precarious situations where teen dating violence can occur. Talk to her in a casual manner and tell her your concerns and that you hope that she will rationalize and look out for her own welfare at all times.
If you’ve had any experience with teen dating violence, then you know how damaging it can be. Most teen experiencing this sort of violence may not even be aware that it’s wrong. Teasing, name-calling and other negative behaviors may be seen as normal, but they are clear warning signs of potentially abusive people. Younger siblings may have to learn this for themselves, but talking to them about what to watch out for may help. Have a conversation about how teasing may lead to more serious behaviors later on, and check for signs of depression or anxiety, as they are common among teens experiencing dating violence.