B2 visa extension rate of approval or denial in this recent time

[Dishasc16]

Hello,
i am looking to extend tourist visa for my mother.
she can stay till July 30th, her tickets got cancelled by airlines.

the visas are getting approved or not....whats the ratio of approval ??

Please anybody could help would be really grateful.
Do not want to invest the money and loose it, its anyways very hard time going for me.