John could be difficult since he's a soldier, he could have been posted anywhere - in theory Anne could have been at his various postings with him.
Based on the children's years of birth and date of marriage for John and Anne, it would appear that she is likely to have been born any time before about 1838 (i.e. age 18 at marriage). She was alive up to at least 1865 when that youngest daughter was born, so give some sort of date window for a death search. I'm guessing she died before 1901, as a quick search of the census showed no likely matches, but worth double checking that...
Assuming she died in the same area of Dublin city as those baptisms and her marriage, i.e. Dublin North, then there are a few matches for her death that are worth following up to start - see : here (FamilySearch).
a few of the possible matches :
Name Anne Boylan
Event Type Death
Year 1866
Registration District Dublin North
Age 32 (est. year of birth 1834)
Volume 12 / Page 379
Name Anne Boylan
Event Type Death
Year 1875
Registration District Dublin North
Age 38 (est. year of birth 1837)
Volume 2 / Page 586
Name Anne Boylan
Event Type Death
Quarter and Year Apr - Jun 1892
Registration District Dublin North
Age 54 (est. year of birth 1838)
Volume 2 / Page 453
Confirming matches for death certs is much more difficult than baptisms or marriages as they dont include much detail, but the addresses and the name of the informant can sometimes help confirm a match. Certs for women can mention husband's occupation which could help in this case also. It can often require ordering a number of death certs to try and find one that matches the correct family, even for the less common names.
The Glasnevin website is at this link , and there are quite a few Boylan entries listed. The details they have are burial records for the plots, and can include family groups. I think it would be be better to narrow down a possible date before starting a search of these.
There are Memorial Transcripts (i.e. Headstone Inscriptions) and photos for Glasnevin on the IGP Website, but note Glasnevin is a very large cemetery and only parts have been covered in this project. (The official Glasnevin site should cover all records, and include burial details for plots even when there is no headstone)