I am so lucky with my 2x DIL, I adore them both, so my heart goes out to you, as you seem to be in a no win situation. Me being me I couldn’t ignore it but of course by responding it could go either way. Personally I would respond to her text on the lines of “ please do not ask me to choose between my grandchildren as I love them all the same”. I would also bite the bullet by asking why you can’t be friends, saying how important it is for children to grow up with love and harmony from all the family. Good luck with whatever you decide, but as others have said, so keep those texts, just in case, and you will have your proof that you have offered the olive branch. Good luck ....