The expression "Ostara" is just simple a mistake of the linguistis "Brothers Grimm". Never existed a Germanic or Celtic godess with this name. And "Eostre" is only another word for the godess "Ostara" who never existed.
Do you read what someone says to you? You can have as many votes for Ostara or Eostre. Many times nothing is still nothing. The expressions "Ostara" and "Eostre" are pure fantasy and do not refer to pagan gods.