Hello and hope you are doing well.
Her symptoms of moving in sleep could be due to a sleep disorder called Periodic Limb Movement Disorder (PLMD). They disrupt sleep and cause involuntary movements during sleep. The cause is not known. They can be diagnosed with a sleep study and medications help to control them. I would advise you to consult a sleep specialist who would assess with first a sleep questionnaire, and then he may ask for a polysomnogram, which is an overnight sleep study as this helps to detect PLMD.
Hope this helped and do keep us posted.
I think it might be a good idea for her to talk to her dr about sleep apnea and have them rule it out. Especially if she snores loudly, is overweight, has any sinus issues, or wakes up tired or with headaches. Sometimes when a person has sleep apnea they stop breathing and it jerks them awake just enough for them to move position and start breathing again. It might not be sleep apnea, but it's something to consider.
It could just be a dream she is having or something else. I don't think it is too serious to worry about but if it really bothers you, you could talk to a doctor and see what they say. Hope this helps.