Sounds like the grass is greener sweetheart, rant on here as much as you like, but I would give you the following knowledge and advice together this in RL:
Firstly, I was a military wife, yes you get a cheap place to live, but if they don't have kids (unless he is using your dd as a headcount) they'll be in some grotty shitty flat, with a 70's kitchen, red carpet and blue curtains. He'll be away a lot, and she will be stuck at home with no prospects, normally in the middle of nowhere, bored senseless.
The housing for his rank will generally be awful. Some patches are also filled with awful bitter jealous twisted women. Rumour spreading is rife, gossip is part of the course. Your life isn't private at all. You never really know where your husband is, is he doing what he says he is etc. It takes a lot of trust. if she is as immature as you say, she will make his life hell.
Secondly, why is this your problem? This is what you should be saying to him. It sounds like he comes round too much to offload about this girl. Why should you have to listen to that? Next time, don't accommodate the conversation. Just say, this is inappropriate, you discussing the woman you are marrying with your ex partner, if you have issues and concerns, please discuss with her. It simply isn't your place, and it's making you feel worse. Distance the visits, he takes dd out, drops her off, make conversation about the next arrangements and then politely close the door.
Thirdly, she is probably insanely jealous of the fact that you have a tie that binds you to this man for the rest of your life. At 19 that is pretty hard to get used to, but surely he needs to be sorting that out with her, for when your dd visits their home?