Bella mentions that she hopes that Charlie will make his own false assumptions about her new looks as a vampire...

She's pale because she's been sick (it's reasonable) and her eye pigment has changed because she's been sick (some diseases can change eye color, so also reasonable). She secludes herself because she's embarrassed. She doesn't expose her skin outdoors because she's paranoid of getting bit again. She's еще beautiful because she's older and it can happen.

The Cullens and Bella plan that in case Charlie asks for an explanation, they can tell him that she got some rare tropical disease while spending time on the island. And that the disease caused her skin to grow pale and her voice to change.