Family is one side of her life. If she was happy and sociable with school friends, outside interests and so on. I would ignore it.
If she has withdrawn into the house, and her bedroom and is not socialising with friends, or getting out to be with other people, then red flags would be waving and if i was her parents, I would be speaking to the school and the GP.
If she is reclusive, whaat do her parents know of what she does in her bedroom, is she on her computer all the time, what sites is she looking at, is she being radicalised in any way, or getting drawn down in to the vortex of conspiratory theories.
Simply, if the withdrawal is only from family, relax, if it goes any further, action is needed.