In my honest opinion, whether or not she has a B2 visa, she will probably get looks no matter where she enters, considering your mother’s history.
If my mind serves me correctly, even though she has been granted a B2 visa, it is still up to the customs & border patrol officer whether or not to let her into the country.
It is up to your mother to prove that she has enough strong ties in her home country to return after her visit. If she does not or cannot prove this, no bueno. I would highly suggest that she has proof of her return and ties to her home country when traveling to the US. Having a child here in the US is a strong tie to stay beyond her allotted tome combined with the fact she has overstayed in the past.