my advice would be - if you really sure you dont want to be together with that sweetheart who gave u a boat - make her realize you are not a keeper - you love to bang women. Would she be ok with that? Probably not, just tell her honey I am young and I am not ready for commitment, has nothing to do with you. I want to be honest, you can be one of my women, but not the only one. delete yourself from all social media - keep messenger only, that way noone can tag you or smth like that with another lady. Just keep say facebook messanger but block your facebook profile.
For the new Lady of yours the boat lady will be ex, so there should be some tolerance on her part.