There IS a difference, there HAS to be a difference because one is her own son and the other one is not. The relationship with Dylan has become far more intimate, much closer and more trusting and comfortable, she has done far more things with him than with Amber's son. Dylan & Sophia have touched each other's bodies far more times, being more naked in front of the other, share the bathtub, a foot massage, being topless, they have already had a kiss or peck with their lips, felt her butt, clasp and unclasp Sophia's bikini and bra and all that while being Mother & Son, the levels of intimacy and limits go far beyond and count more because of the blood relation, taboos are getting broken or surpassed. Whatever Sophia does with Amber's son is based on someone who is neither that close nor related as much as her own son. There's already a love foundation and caring between Sophia & Dylan from Mother & Son to Man & Woman.
So with Amber's son is with a stranger, not someone that special because it could be either him or with Zac, you can substitute the person but the actions can be the same as well as any feelings but one can't substitute Dylan because of the intricacy of being her son and the bond they have always shared.
So maybe yes, the sexual tension or lust could be there and that's humanly normal but it wouldn't be that different if it was with anyone else as compared to Dylan because when it's with someone related the feelings, the connection, the passion and intimacy it's heightened tremendously. Anyone with real and pleasant experiences in incest would probably agree on that.
On the other hand, if this would be true?!
