I am a librarian hoping to help a patron. The patron believes this science fiction/fantasy story was written in the 1960s by a housewife with four kids. The story might possibly be titled "Girl in a Blue Dress" and concerns a ghost, losing an overcoat or sweater, and being unable to cross water. We have eliminated Shirley Jackson, Jack Finney, and Ray Bradbury.
Here's a cover-scan of the first edition. Looking at it might ring a bell in your patron's head. (Or not, as the case may be.)
And here's a summary from Kirkus Review:
The bookless house at 3 Mole Street seems to promise a dull holiday for avid reader Jane Reid who's been left behind while her parents cross the Irish Sea for a vacation in Scotland. But an obliging girl ghost thoughtfully provides Jane with new reading material every night -- bound volumes of the Girl's Own Paper, E. Nesbit's Five Children and It, and other favorites of a bygone generation. Jane eventually discovers that the ghost is actually Mary Quinton, a fellow bookworm who pined away and died in the very same house after being orphaned at age 13, but Mary evaporates after the return of Jane's father with a suitcase full of Jane's own books. Slight, wistfully sentimental bedtime reading for girls like Jane who won't demand more than a shade of a story.
But I'm not sure that this is what you and your patron are looking for. Let me list a few points to consider -- some of them encouraging; others not so much.
The title is very close to what your patron remembered. Four words out of five match, and are arranged in the same order.
The timeframe is pretty close. Published in 1973, instead of a few years earlier in the 1960s.
The story was not published as a "short story," but as its own juvenile novel. (160 pages according to ISFDB, although that seems to mean considerably less words in total than would be the case in a 160-page mass-market paperback novel aimed at an adult audience.)
There is, in fact, a ghost as a key character. (A young girl wearing a blue velvet dress and lending books to Jane.)
In a quick search through the text, hunting for the word "water," I didn't find any reference to the ghost (or anyone else) being unable to cross water.
Other searches failed to turn up a lost or stolen article of clothing as a key plot point, although there is more than one occasion when one kid or another needs to change into dry clothes after getting wet and dirty.
The book was purportedly written by a woman, although it was actually by a man. I have no idea how far that deception was taken. For instance, was there ever a bit "about the author" at the back of an edition of the book, or published somewhere else around that time, which might have led the reader to believe that the author was the mother of four children? I don't know, but it's conceivable that the answer is "Yes."
A note: In case your library doesn't have a copy gathering dust on the shelves, I discovered that In a Blue Velvet Dress is available for people to "borrow" (digitally speaking) and read for free on https://OpenLibrary.org -- so looking at the actual text would probably be the best way for your patron to determine whether anything about this book seemed suspiciously familiar.