Mingram
I have a Rubies Jango helmet that was already painted as a custom Mando so it would not be a shame to do that again in the color scheme your daughter wants. I tried to sell it earlier this year but it ended up not working out.
The Rubies Jango is the smalles Mando helmet that I have come across (not saying there arent smaller ones, but this is to my knowledge only). It should also be much smaller then a GMH.
How old is your doughter?
Id say it would make a great custom Mando for ages 6 to maybe 14. Younger then that and the weight is going to be an issue, older then that and you'll start outgrowing it.
If you are interested I can give you more details.