OP,
This sounds like me.

I never had any relationships and when I married my husband, he had has his fair share. He was involved with his ex for a while and it wasn't working out. We ended up meeting, falling in love and getting married. I was the first he could ever think of marrying so the love was genuine and we were perfect for each other in every way.

I kept holding to the past, sometimes asking about his ex and once found a dairy and some pics. It broke my heart.

Being a very independent and confident person, this feeling was very foreign. I had never been the jealous type. Then I realized I was really in love and this feeling brought a slew of emotions with it...jealous..insecurity ...and so on.

What I wanted from my husband was love, patience, honesty and reinsurance that I was the one. He tried and made the effort. I am very vocal so I told him all along how i felt and what he needs to do to make me feel better. 2 years down the line, it has all gone away.

My suggestion is if the ex is the only thing that is troubling her, be patient. When she asks about her, tell her how you felt and how its over even if it sounds repetitive. Make the extra effort . I know how it feels to see pictures and reminders (in your case you were married, same house...etc so I can imagine how worse she would feel)

and hopefully one day it will be over for her. You may feel frustrated and irritated but you have no idea how it feels to be on the other side and deal with this (it is very very hard)

PS: Sometimes there are rooted insecurities from past (dad wasn't faithful...etc). She could help from counseling if you feel its gotten out of control