Nepali daju-bhai didi-bahini haru,

Need some suggestion on the process of extending a visitor visa (USA).
My mother's here and I want her to stay couple more months, prolly 6 more months.

I got the basic idea of the process--apply 45 days b4 the date on i94 (which in my mom's case is mid june), $290 USCIS fee (i think) but need a little more assured suggestion on the required documents. 

And has anyone used USCIS ELIS yet? Is it much more convinient than just applying with paper documents?

Any advice or suggestion will be appreciated!!

dhanyabad!