1) The potion that she drank turned her into a two-year-old, but did not cause any other changes. She has retained whatever skill she had before she imbibed the blue stuff.
2) Your corpses decomposed. Since there were no living adults left to bury them, they don't have graves.
3) You could get lucky. There are several Island Events that could bring your lone survivor some company (and even a potential mate). They are random, however they have a higher likelihood of occurring in adverse circumstances such as yours.
