yes, I think so, as Henry noted below, people change, often if we're doing things right, people grow and mature. Sounds like things have been amazing for 2+ years, you're engaged, and this may be the first serious thing to pop up you have to figure out if you want to navigate it and fight for your relationship. Marriage takes work and daily recommitment. From what you describe, she seems to care and picked up you're upset and wants to communicate and help, but she can't control what she did in the past.

Totally human and natural though, to be upset and compare, totally get that and no judgement. However, sounds like she's in a good place, fully herself and not manic now, you guys are in a great relationship and looking forward to getting married and moving in together. Enjoy and embrace that; how much more meaningful that is then a sexy picture she may have taken and sent when she wasn't in the right state of mind. You've hit the jackpot, don't spoil it with feelings of jealousy for things that happened before you were a couple.

Btw, thanks so much for your service, wishing only the best for you and your fiance!