Paul, follow the same steps that I showed you for Jane Ann Clarke.

You wrote: Census 1891 piece 4684 Folio 49 states: Daughter of John Wade aged 12, living at Loughcroute, Jurby, Born Jurby.
Answer: Have you checked the 1881 census where she would be aged 2?
www.familysearch.org/Eng/Search/frameset_search.asp?PAGE=census/search_census.asp

John WADE Head M Male 30 Jurby, Isle of Man, England Ag Lab
Christian WADE Wife M Female 27 Andreas, Isle of Man, England
John T. WADE Son Male 5 Jurby, Isle of Man, England Scholar
William J. WADE Son Male 1 m Jurby, Isle of Man, England
Mary E. WADE Daur Female 8 Jurby, Isle of Man, England Scholar
Eliza M. WADE Daur Female 4 Jurby, Isle of Man, England
Annie L. WADE Daur Female 2 Jurby, Isle of ManSource Information:
Dwelling Killeys Cottage
Census Place Jurby, Isle of Man, Isle of Man
Family History Library Film 1342345
Public Records Office Reference RG11
Piece / Folio 5598 / 108 p. 7

You wrote: I also have her down as being born in Andreas? with a date of birth OR bapt Mar 18th 1879. and her mother being Christian Cowley

Answer: You need to give your sources for the information you have, so that it can be seen whether or not they are authentic.
The above census has an entry for William J. WADE aged 1 month which is as close as you could get from censuses to find a birth date and the parents.
Therefore the next step is to look at Brian Lawson's birth regt indexes:
www.iomfhs.im/lawsons/births/_bir_index.html
These have:
Name Date Par Page Father Mother
WADE, William Joseph 14 Feb 1881 And 22 WADE, John COWLEY, Christian
Then look for other entries with the same parents: e.g.
WADE, Annie Louis 18 Mar 1879 And 7 WADE, John COWLEY, Christian
WADE, Christian Isabel 9 May 1885 And 54 WADE, John COWLEY, Christian
WADE, Easther Jane 18 Apr 1890 And 87 WADE, John COWLEY, Christian
[and others]

You could order the one for Annie Louis from the ref. given, and this may give a clue as to why they were registered in Andreas, but apparently born in Jurby.

You wrote: I do not have any information if she married or when she died, as also her rest of her siblings.

You can find her siblings from the birth regts above, and from the 1901 census - up to that date. After that you need to use the index volumes at the Registry, and also for her marriage if she married after 1901. You may find her burial in Brian Lawson's burial indexes, with the full transcripts in FHS volumes.
I cannot see her in his marriage regts index:
www.iomfhs.im/lawsons/marriages/w_mar.html

Sue