Multiple Visa To Join Parent

I obtained my Indefinite Leave to Remain in UK last November 2011 after my ILR , I applied my daughter who was born outside the UK to join me here. Last 2012, she was granted with a multiple visa to join parent but her visa is valid until August 2014. I was naturalised British Citizen last February 2013. My Daughter is under 18 years old, her DOB is 19/03/2000. She will be 2 years this coming May and she is studying here in UK. I just wanted to know if she is eligible to apply British Citizen using MN1 form? Or what do I need to apply for her for I am the parent with sole responsibility for her.

Any help would be very much appreciated.

Thank you very much!

Best Regards,
Mari