urgent help required (Applying family visit visa for my mum

Hi everyone,

I am a full time student here in UK. and i want to bring my mum on a family visitor visa. She has visited me in 2012.
She is maintaining sufficient funds in her bank account. She is a retired professor so she is earning pension plus she is also working in a private institute.
Her hotel booking is done, plus her ticket is reserved as well.She also has her holidays letter from her employer.
Now all i need to know is that, since i want her to apply for a 2 years visa so she can visit me again without going through all these procedures. 'what she should mention in the purpose of her visit column''? is it ok to say that she has visited me two years ago and now she wants to see me again?
and what she should say about her applying for a 2 years visit visa?
Please give me your kind opinions
Regards