Irish citiznship without father on birth certificate

My Girlfriend is a US citizen. Her father is of argentinian and irish descent, his mother (her grandmother) was born in Ireland and is an irish national.
My girlfriend wishes to take up irish citizenship, yet her mother refuses to allow her father to be on her birth certificate ("he wasnt there when you were a kid, why should he deserve to be on your birth certificate").
So my question is whether she would be able to claim citizenship by proving her father is her father via DNA test. Or else if there is a way of getting him onto her birth certificate, that would not include her having to go to court over it (thats what shes been told she would have to do as she is over 18).

thanks.

How old is your girlfriend?

23

i think you can contact dolphin house,family court they will deal with your enquiry full private and confidentail.good luck

Even if all parties live in the US?
Does this mean she is expected to go to court to settle it?

joshyboy133 wrote:23

Then why is it her mother's decision as to whether her father is named on her birth certificate?

Well as far as I know she needed both of them to ratify it and to say he is indeed her father.
Otherwise how would you prove that the father of the child is indeed that person?
If anyone knows the procedure for what someone in this position would have to do in order to get her father on her birth certificate, please help me out.
She is moving to the UK in 1 month and therefore will not able to do anything with her Dad for the year that she spends over here. So I feel she needs to resolve this asap or else she probably wont be able to do any of this without her father in attendace right?