How important is the syllable rule for naming?

Felicia
The name we like the most for our daughter right now is all two-syllable names. My mom thinks we ought to reconsider it because it doesn't follow the syllable rule. The name we like is Leah Diane with our last name being two syllables. I'm not finding many other options that we like that aren't two-syllables or repeat sounds from Leah. No, I don't want an Ameilia Bedelia type name, as cute as that is! And Leah Ann feels weird to me. Our son's name has a pattern of 2-3-2 syllables, which apparently is more desirable.