Dang Jewish Witches showing up us regular witches.
All joking aside a curse is a curse, the energy comes from the same place regardless of the witches title. Anyway, cleanse, protect, and ignore. Curses get stronger with belief, it could be very possible this witch just said they cursed your friend, and your friend took unrelated events as proof there was a curse. This caused worry and fear, which welcomed negativity, and unknowingly to your friend, she cursed herself.
If you are all worried, cleanse yourself [sea salt bath, visualize the water washing away dark tar like energy stuck to you and when you pull the plug taking the energy far away.] Then cast a protection spell, and move on. Daily shielding can also help, but don't worry about curses.