I am a naturalized US citizen. My parents live in India. They hold multiple entry visitors visa for the US.

I recently filed for their I 130 (as parent of US Citizen) with option for consular processing. Their petitions were approved and I got I 797. However, a few days later, I got I 797 C for my mother stating that State Department has requested the petition to be reviewed. There was no objection for my father and Dept. of State has already contacted my father.

I have 2 questions:
1. Can my parents visit US this summer using their visitors visa?
2. What can we do to speed up review of my mother's I 130?