Thanks for your reply.
If she is jointly named on the title to the property then you cannot transfer the title and remortgage without either her consent or an order from Court stating that the title should be transferred.
If she has maintained her share of the mortgage payments until a couple of months ago and there is no deed (eg, declaration of trust) confirming that you hold your shares of the equity in specific percentages then there is a presumption that each party holds a 50:50 share and the onus and burden to prove that this is not the case would be on the party claiming more than 50%. Not paying the mortgage from recently would not do it unfortunately.
If you wish to remortgage (you will obviously need to demonstrate sufficient income to a lender to receive a mortgage offer) and transfer the title in the property then she will need to sign the Land Registry Transfer form and contract. If she does not consent to the transfer you will have to apply to Court for an Order for sale.
Unless she is desperate to be removed then she will likely ask that she be paid for her share of the equity. You are going to have to contact her to check initially if she is willing to agree to the transfer, if she refuses then you will have to see a property litigation solicitor to write to her and make sure she knows that you can apply for an Order. I would expect negotiations as to her share of the equity to start here.
Litigating can be expensive and unless one party is being totally unreasonable and/or there is a lot of equity in the property it is generally better to settle.
Sorry, I'm sure this is not the answer you wished to here.
If this is useful please kindly click accept so that I may be rewarded for my time. You will be free to ask follow up questions.