How to respond to friends of NC parent reaching out

I've gone NC with my mom for about a year now due to childhood abuse (physical and mental). She is apparently talking about it with some of her friends (and with that I mean the NC, and how bad she has it because of that, not the truth about what happened most likely). They have known me since I was little, but I don't know them well enough that I have spoken to them in recent times. They have now reached out to me via a postcard saying that they find it hard for me that my relationship with my mom is so strained, and that you cannot get lost time back. I don't think they know the full extent of the story (actually, I know, because my mom told it to them and she has her way of viewing things. If you've read Adult Children of Emotionally Immature Parents, she is textbook that: no empathy and no self-reflexion). Do you have any advise on what to respond to the post card? I don't blame the family friends that they are trying to mend our relationship, they don't know the extent of the damage that is done, but it has been done and NC is the best option for me.

Edit to add: Thank you for all of the comments! I definitely see what you're saying and I do agree now. I just tend to want to keep the peace and make everyone feel comfortabel, but now I definitely see that this is not okay and not nice at all. Thank you! I will not respond to them.