It was during a training camp in Spanish Alicante that the accident happened.
She was in Spain with the Dutch national team this week and lost consciousness after the collision.
She was then taken by ambulance helicopter to hospital and operated on.
She was placed in an artificial coma and a couple of weeks later she was moved home to the Netherlands.
Now she has woken up from her coma and is conscious.
She can communicate non-verbally, but the prognosis is still very unclear.
"Doctors can not yet say what symptoms will remain due to the brain injury," Pieters' team writes.
In October last year, Pieters became world champion in the discipline of velodrome cycling madison for the third year in a row.