First, I believe the past DOES matter. Past behavior is often a good indicator of future behavior.

Second, her saying she "loved all the attention from men" sounds like a MASSIVE red flag to me. That's someone who enjoys validation. Far too many people who need validation are searching for quantity rather than quality.

Third, it's not insecurities. It's about learning your partner's past. You don't need to justify to anyone (especially a partner) why something in their past bothers you. If it does, it does. It is an incompatibility that is nobody's fault.

Fourth, as emotionally difficult as it may be, LET HER TALK. Gather information to determine if she is someone worth committing to. There are tons of people who are great dating partners but poor life-partners. Breaking up with a dating partner is a lot easier both emotionally and financially.

I'd do nothing... FOR NOW. Continue monitoring, but say nothing. Saying something might trigger a change in behavior.

While this does sound a little different, if you don't see more behavior of this type, you can write it off as a "one-off" and that's that.

However if more photos continue, then you can have a discussion with your husband.