I would be 1000000% cautious here.
You need to build trust and you don’t know her motives so - be v prepared -
assume that every detail of your life will go back to DS - so decide what info you will share about your life, if any.
assume she will be judging everything you say and how you act and will be comparing it to the negative version she has from your DS.
assume she will ask about the situation - decide in advance how or if you will respond - assume your answer will go back to DS
assume she has been sent with a message (maybe not overt) from DS
assume that she might be calling on you to sort something out that DS has done/said
assume as PP has said that the extended family are looking for a reconciliation
Be careful - I hope that it is all with good intent, but certainly not worth losing the distance and calm you have built up over the years.
Maybe head it all off with a statement in your first response - DS and I are NC, I will not be discussing why, not interested in restoring contact and do not want to hear any info about her or any info about me to be shared with her.