It seems you are well aware of the situation,
Since you said internal genitals absent I assume you had your girl scanned.
There are many variants of this type of illness.
Internal genitalia consist of mainly uterus
Uterus is where the womb develops. but ovaries is most important since it is secreting sex hormones.
If your child has no ovaries, she would not develop any secondary sexual organs like breasts, pubic hairs, broadening of hips etc. this can be treated with artificial hormone replacements.
If no uterus but with ovaries, then she cant bear any child.
Her chromosomal analysis should be done since it may also be due to loss of one X chromosome
(Turner's syndrome) if it so i am afraid there may be learning difficulties, many cardiac complications and medical complications.
She may have a normal childhood. Only during puberty
she may need extra attention which depends on the diagnosis.
Hope I am of some help to you