This is quite interesting and I cannot think of any medical reason for it. I do have a suggestion though. Have you tried the pet water fountains that constantly run? I can send you a link if you would like for me to. You could get one of those for inside the house and then your could get the drip spout that hooks to a faucet for outside and maybe she could learn to use it if she likes it since she is so funny about what she drinks from.
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