eerr... mate.. this is actually quite a simple case..
This is child hood trauma. She has being either abused, raped or massively ill treated mentally when she was little.
Basically she does not "trust" married men. So., it could have been a brother in-law, an uncle who was newly married.. etc etc and the list is endless.
There are two way to go about this matter.
1. Talk to her to the "point" ... which means.. initiate the conversation with the line "you don't trust married men isn't it" .. and see if you can take the conversation from there on wards...
2. Doctor - ... I personally do not encourage this as I believe no one can solve other's problems unless themselves.
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Make sure whatever happens that you don't get pissed off or scare her more. what you are dealing with a deep rooted fear or a phobia... so it will be incredibly hard for her to open her self up. So this subject you might have to bring up several times over a long period of time till she feels comfortable to speak about.
This is just like you are talking to a complete stranger about your methods and ways of masturbation and your sickest sex fantasy : )

.. so I hope you got how uneasy would it be for her to talk to you.
so chill the fuck out a little... talk to her from a distance.. don't get too close to her at first... don't force her to look at you.
Or .. find a intermediate object which is non threatening ..... may be adopt a DOG or a Kitten .. and show your affection and care for the animal where she will understand that you are different and you "care" .... and base your conversations with the pup or kitten in the middle grounds.
This is a classic case mate... almost a text book case .. so tread carefully and be patient... people who recover from such mental drawbacks are simply will be like "dogs" ... which means they will LOVE the person who drag them out till death. IF you do it right and be able to drag her out of her fears.... she will will love you like crazy and would take a fucking bullet for you.
so again.. tread carefully... be patient...
all the best !