Tenant is not willing to vacate the rental apartment

My tenant's old contract ended in September 2019, and then when we asked her to increase the rent (as per contract clause) in the new contract, first she denied, but then agreed. However, from October 2019 she stopped paying the rent. After quite some follow up, she eventually payed an amount in November 2019, but that was only 1 month old rent (and not 2 months of Oct and Nov). The remaining payment never reached us, so getting fed up we emailed her to vacate the premises, and gave time till end of Jan 2020. She agreed to vacate by replying to my email and said she does not agree with rent increase. In the meantime, when we asked her to clear the pending rent amounts, she only gave a minimal amount (30%) in Nov, nothing in Dec, and 1 month in Jan (equal to the new contract amount). As we are nearing Jan end, we called her recently asking when should we come to pick the keys. But now she is saying that due to some problem she can't vacate now and need more time. What can I do?