I'm with you on
Cecilia! Though I think mine emerges more as si-SEEL-yə.
Cecelia, I don't know so much. I say
Celia with three syllables, but
Cecelia annoys me so much that I don't believe I've ever pronounced it at all.
Cecily has the "alternative" of
Cicely, which seems to suggest two different sounds. As a pair of sparring partners who end up calling each other "sister", it works well for me if
Cecily and
Gwendolen share a short E sound. But the whole Cec- complex is tricky.
Cecil is CESSil or sometimes CISSil in British English but, apparently, CEEsil in the States, and nobody seems to find this inconvenient: maybe the same applies for girls?