mother hen

Short definition from Wiktionary

Noun

1. 1
   A female chicken who bears eggs or chicks.
2. 2
   An outspoken and overprotective woman or person dealing with others' affairs; especially, an assertive matriarch.

Verb

1. 1
   Alternative form of mother-hen.
2. 2
   To behave in an overprotective or extremely nurturing manner (towards).