Some people I've found in my many years of living have absolutely no filter between what they are thinking & what comes out their mouth. It doesn't mean that it's something they have thought about themselves but could be in general what they think about people who have sex outside of marriage & without any tact, blurt out what they are thinking.

If this in fact is the kind of person she is & you can't handle a person who does that, then I would make the choice to not have lunch again with her.

The fact that she did ask to have lunch with you again may be that she regrets what she said to you & may want to apologize in person as she said it in person, an apology would be appropriate in person also.

Personally I would go out to lunch & bring up the topic that what she said was hurting to you & then from her response go from there as to whether you are willing to continue the friendship.

I guess if it made you feel shame you must have in a way associated yourself with what she said, otherwise you wouldn't have felt shame IMO as we don't feel shame for something that truly doesn't fit the situation. Why does she feel the need to be so brutally verbal about that?.......has that been her personality all along? Usually people don't change so I would think there might have been signs of her being like this before in your being together.....just wondering.

It could be that you end up feeling like it isn't in your best interest to associate with people like her & don't feel bad about not continuing the relationship.