You can see the portraits of her ancestors on the wall - Lord Baydren Gardis and his fox wife Elisia. Their marriage was a real scandal in the society of wolf Tangrion Empire as well as among radical foxes (Alefex was a part of Tangrion back then) but in the end everyone just had to accept it.
Since Gardis family had a hidden gene that let them breed with foxes, Baydren and Elisiana had offspring and their alliance was also a reason why some pups in House Gardis were born as foxes, not wolves. Such as Eliza.
Also considering Eliza’s outfit here. That was her normal look before conversion to naturism. But even though she is full-time nudist nowadays she puts such clothes when she has to visit places where public nudity is not allowed. Or when she simply feels like wearing some cute clothes, sometimes it happens too. When Eliza became more mature she came to conclusion she isn’t obliged to follow strict rules about her appearance, and she can be both naked or clothed, depending on her mood. So if she prefers being stark naked, it doesn’t mean she can’t put on something on occassion.