psuedo step mom

A woman who is smart enough not to get married again, but still takes her partners children under her wing and treats them like her own, giving support both financially and emotionally. She cooks dinners, does laundry, cleans and even car pools. She typically gets no respect from the children until they are adults, but because of her love for her partner, she sees the importance of stepping up, even though she is not a step mom.

"Is that woman who does so much for you your step mom?"
"No, she's not married to my dad. She is my psuedo step mom."