Abel's initial interest in Aries wasn't because she was beautiful or smart or there was anything special about her. What made him take her in as his pet was because of the situation and the place; his mood at that time as well. But other than him, other people like Dexter were only curious about her.
Dexter's interest in her was because she was smart. She picked up things quite fast.
That was why, when he told her he must fool everyone in the manor, Aries spent hours mulling over his words. And then it hit her.
She didn't have to make others believe her. She only needed to make Dexter believe she was Daniella.
It was ridiculous, but not impossible.
People would look at the two of them and would instantly tell they didn't resemble each other. But if she changed her hair color and add a bit of glamour to her usual appearance, they would have similarities one way or another.