Personally, my advice would be to cancel. "Sorry something came up and I can't make it."
Remember, people want what they can't have. She will wonder why you prioritized something else. "Is he moving on? Am I ready for him to leave me behind?" Those kinds of thoughts can stir up of feelings of "Oh no he dint! HE AIN'T GETTING AWAY THAT EASILY!"
Read the distance-pursuit thread.
If you do end up going, my guess is that she is seeing this as two friends having dinner. Not sure about you, but I wasn't interested in friendship with my WAW.
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018