It is rather an expression that we use in the form of affection for someone (woman). though grammatically it can be said that if a combination of these two words Es más bien una expresión que utilizamos en forma de afecto hacia alguien (mujer). aunque gramaticalmente se puede decir que si una combinación de estas dos palabras nota: nos siempre se le dice a una hija, también esta expresión es dicha por hombres hacia su pareja, por lo menos aqui en México

It is one of the most common words used here in México, You call MIJA to any women you feel affection for, it is a sweet way to call them except to you Mom that would be weird but here are some of them: - sister - daughter - girlfriend - wife - co worker Note: You can also use MIJO with men but only to your husband, boyfriend, son or someone younger than you, and just when you are a girl, if you are a boy you don't have many options to call someone MIJO unless your are gay and call your male friend or boyfriend like that but not to your dad or brother or friends if you are straight lol. Also dads or Granpas can use it with their sons or grandsons. In conclusion is mostly used from women to other women (mija) and women to other men (mijo). In a few words is for showing lot of affection but nowadays is just more like a tradition, you say it without notice the meaning you just let it out automatically.

Its a very informal way to call someone. you use it with any woman, not necessarily with your daughter.

tambien es usado en Argentina, aunque no es muy comun. Lo he visto escrito "m'hija", no "mija". Obviamente es una contraccion de "mi" + "hija". Y tambien existe "m'hijo"

This is not popular here in spain, but I have friends from Puerto rico who use this expresion.