what does "got a touch"mean?
He saw the scar from her surgery running up her left arm at the elbow—deep trenches, he thought, as in the basement. Scars on what was his, what he loved, what he needed to protect.
“On an inhale, lean left. Don’t overstretch, Hester.”
“You’ve got me doing old-lady yoga.”
The annoyance in Hester’s voice made the whole scene marginally less weird.
“We’re taking it slow. Breathe here. Inhale, both arms up, palms touch. Exhale. Inhale and lean right. Both arms up. Repeat that twice.” As she spoke, Abra rose to kneel behind Hester and rub her shoulders.
“You’ve got a touch, girl.”
“And you’ve got a lot of tension here. Relax. Shoulders down and back. We’re just loosening up, that’s all.”

Question

what does "got a touch"mean?
He saw the scar from her surgery running up her left arm at the elbow—deep trenches, he thought, as in the basement. Scars on what was his, what he loved, what he needed to protect. 
“On an inhale, lean left. Don’t overstretch, Hester.” 
“You’ve got me doing old-lady yoga.” 
The annoyance in Hester’s voice made the whole scene marginally less weird. 
“We’re taking it slow. Breathe here. Inhale, both arms up, palms touch. Exhale. Inhale and lean right. Both arms up. Repeat that twice.” As she spoke, Abra rose to kneel behind Hester and rub her shoulders. 
“You’ve got a touch, girl.” 
“And you’ve got a lot of tension here. Relax. Shoulders down and back. We’re just loosening up, that’s all.”

Answer

It is implying that she is good at touching, so in this case it means she is giving a good shoulder rub.

There are actually two subtly different ways of interpreting this sentence, even though they end up meaning the same thing.

1. Having a touch for something means you are good at it. "You have a touch for cooking" means that you are exceptionally good at it, and implies that you have a sense for how to cook well. 
So in the text it could mean that whoever is giving the shoulder rub "has a touch for shoulder-rubbing", and the shoulder rub is good.

2. The second way to interpret this is that it is an exclamation about the physical touch itself, not the metaphorical touch of being good at something. This would be similar to saying "You've got a temper" which means that you have an exceptional temper. 
So in context, it would be an exclamation of how exceptional the person's touch itself is, meaning that the shoulder rub is good.

Either way, it is a good shoulder rub.