noun
teenage mother
Refers specifically to a mother who is still in her teens, often with a nuance of youth and inexperience.
彼女は17歳でギャルママになった。
She became a teenage mother at 17.
noun
young mother with gal style
Describes a young mother who maintains the flashy, trendy fashion and makeup associated with the 'gal' subculture, even after having a child.
あのギャルママはいつも派手なネイルをしている。
That young gal-style mother always has flashy nails.