That doesn’t sound normal to me. The head tilting could be a number of medical things, which could be affecting her drinking, or they might be unrelated. I think a vet visit is in order for sure. You can try “skin tenting” to check if she’s dehydrated. Grab a firm handfull of her scruff and pull it up a bit (don’t actually pick her up, just grab the skin, if that makes sense). When you let go, it should snap back quickly (you can compare to your other bunnies if that helps). If it kind of rolls back into place slowly, she’s dehydrated.
Can you offer her some very wet greens to try to get some extra water in her? You could also syringe her some water.
In any case, yes, please see the vet.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.