When she closed the account, if any money was transferred to her separate account, that would have been crminal embezzlement, civil conversion and breach of fiduciary.
If she wanted to start a new business and renew the lease without you, that's a breach of loyalty and if you're injured you can sue for that, too.
You mention that you received a letter from "her paralegal." If your partnr is a lawyer, then that's okay, otherwise this paralegal is practicing law without a license and you can sue the paralegal for fraud -- or, just call the State Bar of Washington and report the paralegal.
There is no merit to the claim that you abandoned the business. That's like saying you have no claim to your wallet just because one half of the contents belongs to your partner. Totally frivolous argument.
As far as your incurring legal fees to deal with this, I have no solution, but you can get them back from your partner, assuming that he/she has any money to pay with.
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