Acquantiance pursuing my ex

I am so mad. I am 39 (F) discovered that my ex (40M) is being pursued by an (48F) acquaintance who have known me from the inception of our marriage. She has always been overly friendly w my ex. Apparently she was patiently waiting for the divorce to pounce. She is downgrade in all aspects. I wonder why there’s some women that have no honor and would date somebody’s ex.

I feel like calling her and going off on her for being such a POS of a person.