I don't know the dimensions of your tank but I would say at this point you can do one of two things.
Remove some of the rock work to make more swimming room for the tang or find her a bigger home - good reason to buy a bigger tank!
Making more room for her is only a temporary fix but it might buy you enough time to set up another system for her.
Honestly, all of my tank decisions are based on my tangs and what they need and what is best for them.
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