mother surrogate

moth·er sur·ro·gate

one who substitutes for or takes the place of the mother.
References in periodicals archive ?
Finding its roots in her deprived childhood (ironically frozen out of her own family in the way she would be by the Windsors), Simpson was a manipulative social climber who, while on her second husband, calculatedly set out to win Edward and make him, weak of will and with a mother surrogate obsession, dependent upon her.
And since they are used to taking whatever they need in life, these two smart scavengers adopt a similar approach to this mother surrogate.