Can someone please explain what the hell the last 2 eps of Dr Who were about?

she had been the terminally ill niece(I THINK !!)of Mr Lux...they SAVED(as in SAVED on a computer)her by making her into the computer which is running the library.when the Vashta Nerada started appearing the little girl(computer)SAVED all the humans in the computer with her...giving them virtual lives and keeping them safe till they could be uploaded.River Song(the future Mrs Who...lol)sacrificed herself....but that bit confused me(why she had to do what she did)so the Doc SAVED her till such time as he can upload her(why that can't be now I don't know).hope i've enlightened you a little!!