Gift from brother to sister - what is the procedure?

Hi,

 My cousin is 45 year old working in UAE. His sister is a married housewife in India. 

Cousin wants to gift 15-20 Lakhs to his sister. I think gifts between siblings doesn't attract any tax. However, what is the procedure to do this? Is there any documentation needed? 

Also the sister last worked 15-20 years back but has never filed tax returns. So if she gets this gift this financial year, would she need to file returns this year & future years.