I much prefer
Sybil.
Sibeal doesn't sound all that pretty to me--which I find odd, because I like a lot of Gaelic names.
I think it'd sound nice with a three syllable name, stress on the second syllable, though. Like...
Sibeal MariaSibeal MarinaSibeal Renata (ren-AH-ta)
Sibeal Vincenta
Sibeal KatrinaSibeal NerissaSibeal FaustinaSibeal AmandaSibeal TeresaSibeal LouisaSibeal Christina
Array