What strikes me the most about Rottytops is how well thought out her character is. A victim of prejudice, which forces her and her siblings to lie and deceive their way through undeath... which only further fuels the prejudice, and so on and so forth with the vicious cycle. It's never shown directly for the most part, but it is implied. She takes an instant liking to the kind, brave and open-hearted Shantae, but her hardwired survival instinct of dishonesty makes it difficult for her to form any meaningful attachment, not helped when Shantae, naturally, is upset by her betrayal. It's only when she discovers Rottytop's true feelings in the Village of Lost Souls and then assures Rottytops that their friendship is genuine that Rotty feels she really does have a chance to turn a new leaf.
Half-Genie Hero then shows her making genuine attempts to help and please Shantae, with her blunders being more honest mistakes then more attempts at manipulation. And during Friends To The End she not only gets a chance to return the favour of true thought-probing by revealing Shantae's hidden knowledge of her human form, but also learn to appreciate her other friends. Sky in particular, going from the person she mutually hates the most behind Risky, to putting in her own words that she considers her to be a great leader.