Hi Jamie. I agree that this is a difficult thing to put into words. I would tell her how much you enjoyed the Mexican restaurant and nail salon. Something like, "It was such fun to go ____(restaurant) and ____(salon) with you and the girls. It was a memorable time. I feel honored that you asked me to participate. Thanks for always making me feel special. You are a wonderful friend. Big hugs coming your way, Jamie."
I am sorry you are losing a dear friend. Keep up the spirit:)