This woman is ignorant of Christianity.
Were she speaking to a Jewish audience about not eating shrimp, then her words about following the OT dietary laws would make sense.
Those laws, however, were SPECIFICALLY voided by Divine decision for Christians. This is found in the book of Acts, a central text detailing early Church history. It was affirmed by the Council of Jerusalem. The letters of St Paul are chock full of discussion of it in one form or another.
The only way to be ignorant of Acts is if one is totally ignorant of Christianity.
For this woman the totality of Christianity is, "love one another".
She doesn't realize that when asked what the greatest commandment was, Jesus replied, "And thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind, and with all thy strength: this [is] the first commandment. "
If you accept this commandment then you listen to what G*D has to say, whether in the old testament or the new testament. The new supercedes the old for a Christian but you still listen to both.
If there is not something in the new that totally contradicts the old then there is a good chance that the old still holds true.