It does seem you focus is more shacking up with your girl friend.
She might want to investigate job prospects in Holland a bit as well in her circumstances.
Putting aside the logic of marrying someone you have only been with for a few days I think even Manilla might find this a stretch.
Why do you not want to spend time together?
Presumably Ireland?
Not sure how many here are familiar with Irish Criminal Law, from a practical perspective the decision will be made at the interview, if a waiver is needed.
The K1 has many disadvantages but not in relation to this.
A 12 year old should be looking at a B2.
Let her parents apply for the visa and yes you will need their permission for you to travel with her without them.