Julie Sayles, 59, is alleged to have persuaded Edith Negus, who was in her care, to leave her estate to her.
Ms Sayles, of Sewerby Road, Bridlington, also bought two houses with money she allegedly took from a joint bank account she shared with Ms Negus, Hull Crown Court heard.
Ms Sayles, who worked for an elderly-care charity, denies fraud.
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Ms Negus's neighbour Jennifer Booth told the court she heard Ms Sayles shouting "I want you to make a new will leaving everything to me and I'll make sure the people you want to give anything to, I'll give them it".
Defence barrister Peter Byrne put it to Mrs Booth she had actually overheard Ms Sayles saying to Ms Negus "if she wanted to leave her her estate".
Mrs Booth replied: "She didn't say that. She said I want you to leave your estate to me".
The court also heard from Brenda Towers, who used to volunteer at the charity.
Mrs Towers said she was asked by the defendant to sign the new will as a witness, despite having recently had a cataract operation and being unable to see properly.
She claimed that she could not remember the contents of the will and did not know that Ms Sayles was to be the main beneficiary.
Ms Sayles was arrested following Ms Negus's death in October 2014.
She told police the centenarian had offered her money for her care and to invest in property and that the wills were created on Ms Negus's instructions.
Sayles is accused of fraud by abuse of position, buying properties with the proceeds of crime, making a fraudulent will and presenting it to a solicitor.
The trial continues.
A carer accused of stealing almost £290,000 from a woman, 102, told her to change her will, a court heard.