i started a new game and a lady villager drank a blue liquid and turned into a kid.she kept her stats but turned into a 4 year old has this happoned to any one else.

Yes, that's a common result of that Island Event. There is a side-effect, however, that won't be apparent until she has a child: she will not stop nursing her child until she reaches the age she was when she drank the liquid. So, if she was age 40 when she drank the liquid and has a child when she once again reaches age 18, she will nurse the baby until she is 40.