Thank you for your query.
By your description two things are evident:
1. Your daughter has this funny sensation only in school and does not happen all the time.
2. Your mother-in-law has restless leg syndrome
Though you mention that your daughter is not distressed but the feeling happening only in school must have some relevance to things in the school. May be some peer or school pressure may be troubling your daughter. After all these possible school environmental causes are eliminated will one consider it as a restless leg syndrome.
I hope I have answered your query to your satisfaction.
Wishing your daughter all the best.
Rajiv K Khandelwal