Yes if otherwise eligible she may do so.

Contact NVC directly to inform them of this and get more info about the request.

It should be within 2 months but likely longer.

Yes you should bring tax returns to interview.

Yes it appears the answer would be affirmative.

You can obtain an extension at a USCIS service center.

Best to contact an immigration attorney for private consult.

More information is needed as home visits are generally not conducted for this.

You will need a cosignor or can use your assets if appropriate. Cosignor is better.

Best to have an attorney review filing and assist with refiling.