No, leaving will be fine but overstay will be noted and may result in issues the next time she wants to apply for a visa or reenter the US.
I am a lawyer but I am not your lawyer unless we have spoken and we have entered into an attorney-client relationship. Due to the nature of this forum, I often do not have all the information required to provide legal advice. Accordingly, my responses on Avvo are intended as general and not legal advice.
Most likely not. However, visa will automatically be cancelled, and depending on how long the person has overstayed, exit might trigger unlawful presence bars, so consult with an attorney before leaving because he/she may have problems coming back.
The above is general information only and should not be construed as legal advice or creating an attorney-client relationship.