visitor visa extension

[visitor_visa]

My mom is here on B2 visitor visa and her I94 is valid through June end. I am planning to file an extension and have the following questions:

(1) If her I539 extension is rejected before June, can she stay legally through current I94 expiry of June end, or does she become illegal in status as of the date of rejection letter?

(2) The 539 is pending and she leaves by June end and subsequently the extension is rejected (say in July end). Because she left before I94 expiry, does the extension rejection void her visa? What if she stayed through mid July thus leaving while application was still pending?

Is there any benefit of efiling the extension vs. applying by mail?

Thanks a lot for your help.

[immihelp]

You are very unlikely hear from the before June. Therefore, your questions are not even applicable.

But anyway,
1. She can stay till the date in I-94 form.
2. If she leaves before I-94 date, her visa is still valid even if extension is rejected. Her visa is void if she is still here past her I-94 date.
3. There is no difference in eFiling vs paper form.