I do agree that rather than whiny I'd say a little too cautious despite Petal's constant reassurances she's an adult and is fully able to consent to progressively further sensual play leading up to and quite eventually crossing that line.
I do like how the Uncle was able to provide his advice pursuing these types of taboo relationships and even the introduction of a possible love triangle with the ex-wife struggling under the weight of her own secrets while still possibly in love with the MC and what that means for own daughters.