Are we discussing direct debit from your mother's current account or for a separate account that money is put into each month for paying bills?
I can well understand your mother if bills are being paid from her current account, as she probably feels she never knows exactly how much money she has in it.
If you set up a separate account, having worked out what exactly is being paid by direct debit from in in the course of a year and transferring a 12th of that amount from her current account on the 1st of each month, she might just be willing to accustom herself to is, and save the expense of paying by cheque.
Obviously, you or another family member need to discuss this at length with her, and perhaps help her tackle internet banking as well.
My mother had always paid all the bills from her cheque account, but a month after her death, Daddy informed me that on the advice of his bank, he had set up a direct debit, as thus he was certain nothing would be overlooked, which as he truthfully said was likely to happen if he had to pay the bills. It worked well for him, perhaps because it was entirely his own decision, which I heartily endorsed.
I knew only too well that I otherwise would have had to cope with his bills as well as my own! (Said the dutiful daughter!)