Annette:
We would need parents names to try to find a baptismal record for Bridget. I checked the subscription site Roots Ireland and they had eleven Bridget Keogh baptismal records in Co. Tipperary from 1840-1847 (ironically none in 1846) and Roots does not have all the South Tipperary RC parish records.
Let us know if you have the parents names or any other clues about Bridget Keogh.
Roger McDonnell