After the death of her parents in 1811-1812  Marianne lived at Wharf House, the home of her sister and brother-in-law, Bridget and John Curtis Byles at Henley-on-Thames.

In 1820 she moved to the home of her sister at St. Aldates Oxford. This move was occasioned by the death of Esther's husband, James Philip Hewlett. Esther's tribute to the care and support of her sister at that time is moving "Her tender sympathy and counsel often ministered balm to the wounded spirit, and in the moments of deepest depression encouraged hope and confidence in God.  And, at the same time her kind and active attention in domestic affairs, left the mother at leisure to pursue those avocations which, under the blessing of Providence, proved the efficient source of support for her dependent family".  Thus, Esther was free to pursue her career as an author enabling her to financially support herself and her children.

For most of her life Marianne suffered from deafness, as did her sister Bridget. It marred her enjoyment of church services and she wrote of this saying "I often realised that (God in present when two or three are gathered together) even when I scarcely heard a sentence of the sermon; it is very, very trying, not to hear all that is said, but the Lord enables me to enjoy much in the reading of the Scriptures, and singing the hymns with the help of a book.  Beside, if I catch but a word or two of Scripture, I can go on with the sentence, and often find it very delightful".

In April 1825 Marianne mentioned to her sister Esther that she had observed a "small tumour on her breast" which had been there for a year or more.   Esther was very concerned about this and arranged for her nephew, Samuel, the eldest son of John Curtis and Bridget Byles, who was practicing medicine in London to visit Marianne at Henley. 

On 9 May, of the same year Samuel made a home visit, made a diagnosis, and recommended immediate surgery.  At 2 p.m. on the following day part of her breast was removed, without anesthetic, and Esther provides a graphic account of the procedure.  ""With every direction of the surgeons she minutely complied, but when the proposed to confine her hands, she said, "No, no, let me hold dear Esther's hand, that will be quite enough; God will support me".  She even declined having a handkerchief thrown over her face, saying, "I am not afraid to see what you do", but on its being recommended, she complied, and said "Well it is of no use for me to see, you know what you are about, God will direct you". 

During the operation, she spoke only once, and affectionately asked "Is Esther here?" I pressed her hand, and assured her it would soon be over; but one small part which had a suspicious appearance it was judged right to remove; this caused a few moments of additional suffering; I explained it to her, and she firmly replied, "By all means do all that is necessary, I can bear it - not of myself. "The dressings were applied, and she was placed comfortably in bed within half an hour from her entering the room."

Marianne spent a month convalescing, after which she resumed her usual activities. However, in June 1825 Marianne's health was again of great concern, a large abscess had formed of the site of the surgery. She moved back to Esther's home in Oxford where Bridget had been taking care of Esther's family during her absence.

For the following ten days the three sisters enjoyed a very special time together. Esther writes of this saying

"I have been often struck to think, when once the children of a family begin to separate in life, how little subsequent personal intercourse can be maintained among them.  In our small family (consisting only of three sisters), this was by far the longest period that we all passed in each other's society from the time of my marriage.  It was a time of sacred enjoyment.  With mingled feelings, we looked back and remembered all the ways by which the Lord our God had led us, to humble us, and or prove us.  Our mercies, both as individuals, and as a family, had been great and numerous; our trials diversified; but strength had been afforded equal to our day; and, on a review, we found ourselves constrained to unite in erecting an Ebenezer to the God of our lives, saying, "We'll praise Him for all that is past, and trust Him for all that's to come."

Marianne's health continued in decline and secondary cancers made their appearance, and Marianne was "parched with pain".  She returned to Henley, and one day while walking with her niece Emma she fell and broke her right hip.  For the remaining twenty-two months of her life she remained in bed. Esther last saw her on 7 April,  and she died on 17 April, 1828. Marianne was laid to rest in the family vault under the Henley meeting house.