my version is 'sentimental sentimental girls'
What does Goo Goo Dolls mean?
Frankly, I don't tend to read it as having much meaning, but "goo goo" is something that people say to babies, and that babies supposedly say. And you're right that doll can mean girl, but in connection with "goo goo" it makes me think of baby dolls.
"Goo goo" is how the sound that babies make is often rendered. There are dolls that imitate baby noises. Hence, "goo goo dolls".