Hi, nurse here. You don’t need to get her plan B. Sperm can’t live very long outside of the body (we are talking like seconds here). She is not pregnant. 16 is old enough for her to go to a planned parenthood in or around your area and get birth control. There also apps that could do this as well. Planned parenthood also has online resources that can help answer your questions better than a google search or a reddit forum can! It’s awesome to be getting ahead and learning about safe sex practices though, good for you. Condoms are cheap though, but not as effective as 2 methods. I would suggest using condoms and pulling out to prevent pregnancy if you can’t access other birth control options.