Foreign national tenant - cancelling agreement

Hello I need your opinion on below situation. Registered rent agreement has been done with Korean Clinet’s company. Possession date was March 1, 2024. Agreement happened on 2nd March. On March 2nd during handing over we asked if they required the fresh paint in the house, she said yes for paint. That time she kept some of deliveries of goods in the flat. We initiated the whitewash work. Meanwhile she made the 3 duplicate keys without any consent. On March 7 we informed her to check the apartment as paint n cleaning work was completed. She said okay. On March 8, she said that will deduct the rent of 8 days due late handover, to which owner said no. As agent I suggested her to deduct the amount from our brokerage to which she denied. And got upset with whole Situation. Later she said she wants to cancel the agreement and wants refund. We informed that agreement has been registered and can not be cancelled now and agreement cancellation clause shall be applicable. Client used absusive language with us and created Lods of trouble at society office. However after speaking with owner she transferred the advance rent, n paid our brokerage after subtle invoice. We completed the paper work, society allowed her shifting and her furniture has been moved inside the apartment. After that she stopped responding to calls emails we sent to her for confirmation about apartment keys and other stuff. But she is not responding. She again sent the email for cancellation of agreement and demanding refund of deposit + rent + brokerage. We are trying to reach out her to resolve the issue but not getting any response. Now owner is getting upset with this behaviour of her. Kindly suggest what should we do?