It's claimed Fr John Lochran said: "will you stop rustling!", as Frances Haler, 87, folded her hymn sheet up.
The woman, who also suffers from leukaemia, is a regular at St Winefride's Roman Catholic Church in St Asaph in Denbighshire.
Her daughter Toni Bewley told the Daily Mail she confronted the priest after mass.
She claims Fr Lochran told her: "It's my church", and suggested her mother take Holy Communion at a nursing home instead.
She told the newspaper: "Mum was really quiet throughout the service, and then I got the hymn and prayer book and all the bits of paper. Mum folded the paper in half and held it up close to her eyes.
"He looked up and said, 'Will you stop rustling paper and holding paper up - I'm doing a sermon.' Thankfully, I don't think Mum realised.
"I was absolutely livid. At the end of the service I told him he had publicly humiliated my mother.
"He said he was in the middle of his sermon and he was in flow and it was disturbing him.
"I have got more Christianity in me than he has in his big toe. I've been left very upset.
"I just can't see what justification he had to humiliate her in the way he did. It's so sad, given dwindling congregation numbers, that he could be like this.
"It's made me question my faith. There's no way he can justify such an un-Christian attitude."
The Bishop of Wrexham, the Rt Revd Monsignor Peter Brignall, is investigating.
A spokesman for the Diocese said: "Mrs Bewley, the daughter of Mrs Fran Haler, has been invited by the Bishop of Wrexham to speak with him directly.
"In the meantime, arrangements are in place for Mrs Haler to receive the sacraments, as it is her spiritual welfare that is paramount. She is welcome to attend any Catholic Church."