Slieve s the name for hill or mountain and comes I think from the word Sliabh. The first part looks more like Slieve than Silver, to me anyway. The second part may start with an 'R' SlieveR***
Slieveroe is in the Electoral Division of Pembrokestown, in Civil Parish of Lisnakill, in the Barony of Middlethird, in the County of Waterford.
The Irish name for Slieveroe is An Sliabh Rua
Above from
https://www.townlands.ieGriffiths also has a Slieveroe in Co Waterford but neither family is there at that time.
In the 1911 census (2/4/1911) there are two Johanna Blanches - older 56 and younger 22 as servants in the home/shop of Elizabeth Dobbyn who lives in O'Connell Street in Waterford. Johanna senior shows herself as widow. My experience is that sometimes wedding certificates did not show that the fathers are dead. If this Johanna Blanche getting married is the same as in the census time may have stood still, a little, as she is 22 in April 1911 and also in October 1912. She presumably gave the info to the priest while her employer has completed the census. She may not have wanted to be too much older than her husband!
The name of the church is Trinity Without.As mentioned above O'Connell street is in this parish and this may be the parish church if the younger Johanna working at Elizabeth Dobbyns is the one you are looking for.