Schooling for non EU children. (Marbella)

Hi, can anyone help me with this...?

I'm British, and have lived here for 17 or so years. My girlfriend comes from a non-EU country and is looking to join me sometime this year, with her 14 year old daughter.

Forgetting the language issues for now (the daughter only speaks Georgian and Russian), will she be able to attend Spanish state school?

We intend to get married (and update their relevant visa applications will be required for that). As the spouse of an EU citizen, will this make things possible? Would some type of 'formal adoption', help the process?

Any advice will be most welcome.

Thanks guys!