I found my fiancé snapchatting another girl: Advice?

I recently got engaged, but yesterday I found him snapchatting a girl telling her she didn’t need to cut her hair that he liked it long. Had I not snooped on his phone, I’d never found out. I don’t think this is right, and getting married is maybe not what needs to happen, am i right?

Do you know who the girl was? Are they friends? Could be totally innocent.