Dash can also mean to strike or fling something somewhere with force: the ship was dashed upon the rocks.
I understand what you are trying to say in this sentence but I wouldnt use this word in this context. To dash has more of an extreme and violent feeling to it when wanting to use it in this way/context.
I would rather say:
She drags her digits along the tree trunk.
Even more natural:
She drags her fingers along the tree trunk.
If you wanted it to have a more extreme or violent meaning, then:
She dashes her hand against the tree trunk as she runs through the forest.
I hope this helps a bit!