That is a sad tale of misfortune, Bow -- I do hope that your family's luck has changed since!
As to
Are you from this area Rol or just have an interest?
I take rather a magpie interest in much of N Wales -- a lot of distant family links scattered about, as with us all, including in the Uwchaled area. And every research problem has its own fascination, whether with some personal connection or without.
I live many a league away though, so it is awkward to get to the local record repositories.
Here is another thought on the Sinah problem to be going on with. So far we have mainly concentrated on trying to find her in the later censuses, whether married or still single. But of course we know that she could also have died fairly young. In pursuit that angle, it may be relevant that NW BMD has an 1853 death entry for a Sinah Hughes in Gwyddelwern sub-district -- the local registrar's ref. being ELWERN/04/2. There is no such entry in the GRO indexes, per FreeBMD. On the other hand, the GRO does show the death of a Sarah Hughes in Corwen RD in Q1 1853 (11b 322), the only one all year -- while NW BMD, in contrast, displays no such Corwen RD Sarah Hughes. So the odds of a contemporary mistranscription in, or of, a quarterly return look fairly good.
Unfortunately at that date the indexes do not show ages at death; but local offices are usually very helpful, so it would be well worth ringing the
Ruthin Registrar, quoting the above ref, explaining that you are looking for the death of an SH who would have been about 12 or 13 in 1853, and saying you would like to order a cert -- but only if they would be so kind as to vet the actual entry for you first. No way to know in advance whether she is your SH, but at least that way you can quickly exclude one possibility from your list.
Rol
