This is a temple for the "gramdevata" or the village deity of Betki. It is not a temple for Ravana's wife Mandodari.
The word mandodari is from mand (water) with udar (stomach). It means someone who is born in the water. This temple was built to worship the great human beings whose children were sacrificed in the past to ensure that this village had a flowing stream of water. There is no well water in Betki village so the main source of water in this area is streams. This is how the village started worshiping this deity.
Shree Mandodari Devasthan has completed 102 years of its Constitution in 2013.