I had a mare who took 3 years to become really friendly....and then she was a pocket pet. The prior owners had never touched her or worked with her and she was fearful of everything. I put her in a small paddock, and would go sit with her, constantly talking softly, but continuously -- actually I was reading a book out loud to her, but she never knew.
Her first foal was an inquisitive little one, and actually would leave her side to come and seek me out. So funny -- there was baby getting scratches, and momma scared as could be. But, the baby and I became good buddies, and the mare became more inquisitive about why baby was leaving her and coming to me. Baby was still VERY bonded to momma, but the scratches became very important to get, so she would come.
Eventually, momma became more friendly, and would get closer. I would give momma a treat, but only if she took it from my hand. Between baby and my treat, she came out of her shell and became quite the "pocket pet". A lovely mare, who went on and had other babies for me, and stayed friendly throughout her future pregnancies, and allowed me in the stalls for their births.
I'd just read her a book, keep your voice calm, and touch her when you can. Direct eye contact can be a "challenge" so, just touch her when you can, and look at her nose! LOL
