I would probably say it's the beginnings of arthritis, probably she's having chronic arthritis stiffness which would make sense with the creaky joints and them happening in the morning, before she gets exercise, ie. movement. At 14, no she's not that old but arthritis can very often show up in even 10-year old horses. I would call your vet (your ahead of me since you said you were going to talk to him) and ask him to check her out and see what he thinks. Then you can discover the wonderful and vast world of joint supplements if you so desire.