Visitors Visa for Sister-In-Law living in UK

[kraje]

Hi, my sister-in-law who is married and works in UK wants to visit us as her (and my wife too) parents will be visitng us in Sept.
My in-laws have already got their Visa approved and stamped (thanks to IMMIHELP for all the guidelines).
My wife also works part-time here in US. Do I need to send the same supporting documents for my sister-in-law for her Visa?
Though she is an Indian citizen working in UK (her husband also works in UK) will she be able to apply for US visa from UK?