Hi Annie Liang,
As you jointly own the property but wish for your mother to hold 100% of the beneficial interest in the property without transferring the legal title, then the Declaration may be created to show this.
Please see attached a link to guidance TSEM9520 which outlines the Declaration of Trust, as well as a template:
TSEM9520 - Ownership and income tax: express trusts - written declaration. Please note that a Solicitor is not required when creating a Declaration of Trust, however, it is advised to seek legal advice to ensure your wishes are correctly reflected.
As well as this, it is not essential to send a copy to HMRC, however, keep a copy of the Trust as HMRC may ask to see this in future.
As you are joint owner of the property, you would still be able to help pay for the maintenance fee, although, your mother would only be able to claim as an expense her portion of the incurred expense.
Thank you.