It's perfectly natural that seeing her would bring this stuff up.
This tells me you are a caring, passionate, wonderful person. If you didn't care you would not be the loving person you are.
I have found that those times when I wish I could force myself to get over it are the times when I MOST need to be PRESENT with my difficult feelings.
Sometimes I am fine, sometimes being around new mamas hurts like hell. Sometimes I go numb.
Some good advice I got was to find a ritual to do when I am hurting, and set time limits so I don't wallow. Wallowing has it's place however! Only YOU can define these limits for yourself.
Rituals could include writing, artwork, gardening or some other healing/growing kind of thing.
"Be patient toward all that is unsolved in your heart...try to love the questions themselves like locked rooms and like books that are written in a very foreign tongue.
Do not now seek the answers, which cannot be given you because you would not be able to live them.
And the point is, to live everything.
Live the questions now.
Perhaps you will then gradually,
without noticing it, live along some distant day into the answer."
The abuse of birthing women is such a painful thing...the birthing system is so BROKEN in our culture...there is BOUNDLESS pain that I myself have to set limits around what I can handle, how much I can think about it before the grief just overwhelms me.
Lots of people say "oh get over it, you should be grateful, don't feel (X, Y, Z) or, don't feel guilty."
That's a load of crap.
YOU HAVE A RIGHT TO YOUR FEELINGS.
You have a right to all your feelings.
Books that may help, that discuss healing from birth trauma
Rebounding from Childbirth
A good Birth A Safe Birth
Good luck to you!