IMO, at 22 months, a 4 hour nap is too long. My naptime here is 2-2.5 hrs. I wake any child up after 2.5 for sure as I don't want that to interfere with their evening bedtime which than in turn affects the next day.
I would think that if she is napping 4 hours and still sleeping normal at home that maybe something is up and I would suggest seeing a doctor just to rule out anything. That's a lot of sleep!