In Romanian the feminine proper nouns (names of people, in our case) are ending most of the time in -a:
Maria, Ana, Felicia etc.
Their genitive-dative declension follows the declension of feminine common nouns, thus:
"I-am dat Mariei/Anei/Feliciei"
The feminine proper nouns not ending in -a do not follow this rule, instead they get the masculine nouns declension:
"I-am dat lui Carmen" (the possible form "I-am dat Carmenei" sounds very strange)
The same rule applies for feminine proper nouns of foreign origin:
"I-am dat lui Sarah/lui Tanya/lui Celine etc."