The General Register Office deaths index entry for your Jane is:
Oastler Jane / 52 / 1878 / Jun / Holborn / 1b / 504
From the age given, she was born in 1826. GRO records begin in 1837, so they are no help in finding her place of birth and parentage. A census record, if you can find one , will give you her place of birth as well as any children’s names and ages.
I have a database of births marriages and deaths of Trews in the Greater London area. This has a number of marriages in the likely time frame but cross checking with Oastler I have pinned it down to:
Trew Jane / 1853 / Sep / Marylebone / 1a / 677(?)(I have a question mark against the page number as the on-line image is not clear and the first digit is a best guess).
You should send for certificates from the GRO (you can get application forms on-line). The death record will confirm the husband’s name and give the address where she died, and the marriage record will give the name and occupation of Jane’s father, and her address at the time of her marriage. The addresses may help you find her in the 1851, 1861 or 1871 census,
I can’t help you further than that, and I don’t think you link into my line (though you may do as my family were in the same general area) but do let me know what you discover.
I am copying this to some cousins of mine who are also researching the Trew family in the London area. If they can help I am sure they will be glad to.