My mom has come to US on tourist visa and her I-94 expires on the first week of May. 

Due to Corona Virus, travel restrictions have been imposed in our home country (India). Also we want to avoid the risk of traveling in flights at this time.

Is there an easy way to to extend her stay in the US by one or two months?

I am aware that we should fill [I-539][1] to extend our stay. But in-order to submit the online application it requires a fee of $370. 

 1. Is filing I-539 the easiest way to extend her stay at this time?
    
 2.   If so, is it possible to waive the fee due to the Corona virus
    situation?
    
 3.   After filing I-539 should she wait for an approval to continue her
    stay? Or is the receipt good enough?

Can you please help me with these? Thanks!
  [1]: https://www.uscis.gov/i539online