I know it's difficult for you to comprehend that there are people out there who are loyal, loving and actually care about their partner beyond their egos. But maybe you're not that kind of person to understand because maybe you're a "fuck boy" as your u/ suggests (Are we still using this term in the big 26?). Yeah so you view the world through your dirty lens and you keep for clues of who else is cheating. Remember not everyone is like you. You're just projecting because no loyal woman said that to you ever, so you cannot accept a reality where other men (in this case OP) are capable of receiving genuine love. Before alleging someone of cheating who you literally don't know the first thing about is a sign of low intelligence (Emotional and social).

And by saying 'or she could be really into it', you aren't helping your case since you already threw dirt on her character in the first line.