Am I legally bound to make a rent payment if I'm not on the lease?

Question Details: About 9 months ago, our friend contacted my husband and I to ask us to buy her failing business; she was unable to pay her rent and was in a dire financial situation. She owned an LLC that rented out rooms to a few massage therapists. My husband and I had the idea that the business would function better and become profitable if it was turned into a shared space. Together we entered into a handshake agreement business partnership with a 33% split for each of the 3 of us in exchange for our rebranding the company - new name, business plan, logo, web design, location remodel, etc., all of which we were the sole investors in. Our business was was a co-working collaborative membership-based wellness studio for entrepreneurs to run their business from. Essentially they paid to rent our studio and booked private time on our shared calendar. We had nothing in legal writing of this partnership, no contract of this agreement and her name was not on our LLC or our business license. We had a business account that we all shared and I managed. I did 80% of the day-to-day business operations. Due to her moving to another city, our partner decided to remove herself from partnership 4 months ago; we have an email from her stating this. We were not yet a profitable business (just breaking even on bills) at the time that we separated. Due to this, we all verbally agreed on how to finish the final expenses and who would take what. We also found out the that location we were doing business in was not allowed to have a business as per her lease agreement. Our partner was the only one listed on that lease and the landlord was not aware that a business was being run on his property. He chose not to allow my husband and I to sign a lease with him. We were told by our partner that we'd have to have all of our belongings out by 05/31. I paid for the rent out of our business account from payment from memberships through 04/30. Our partner chose to stay in the space since she says that the landlord gave her an extension of a month to stay, although this was never told to us by him. We also paid for $500 of the $680 damage charges from the landlord and are prepared to pay the final $1200 that is the monthly rent payment due for the month of May. She stayed in the location without us for the month of June and is requesting that we also pay for that month. We are unsure of what our rights and responsibilities are in this situation.

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