Yes Merry, that is the baptism, and no I haven't seen the original.
My aunt, and other more distant relatives, have her down as Mary Ball. One of Mary's grandsons, Susannah's son, was Thomas
Ball Key. His father was Thomas
Blainey Key, and some other family members were given their mother's maiden name as a middle name. Possibly this is where the assumption came from that Susannah's mother was Mary Ball.
I have now ordered Susannah & Thomas Blainey Key's marriage certificate, so hopefully that will list her father's name. Keeping my fingers crossed!