Thank you for your reply. Here's everything I know so far:
According to Ann Connor/Fleetwood's marriage bans and the 1871 census, she was likely born sometime between 1829 and 1831.
Along with the marriage records for her and John Fleetwood, the 1871 census is the other main record I have for her, where she is recorded as living in the parish of St Luke's, London, with her 7 children:
Mary / Thomas / Rosina / Kate / Harry / William / Emma
In the 1881 census, John Fleetwood is living with three of his children in Shoreditch and is down as a 'widower', so it may be Ann died inbetween 1871 and 1881. However, the only death records I can find for an Ann Fleetwood of the right age after 1871 aren't until 1905.
I have however found a record of an Ann Connor of the right age, born in Limerick but living in Shoreditch in the 1891 census, so I wonder if her and John separated and she reverted to her maiden name? There are at least 10 Ann Connor's of about the right age who died between 1871 and 1905 that could possibly be her.
Her name might be recorded variously as Connor / Conner / O Connor in some records (eg. the birth certificates of her children)