The silence is harder to navigate than criticism because it gives you nothing to respond to - with criticism you can push back, but silence just sits there. Your sister's resistance probably combines her own complicated relationship to weight and bodies with not wanting to acknowledge the change in case it opens a conversation she doesn't have the tools for. Some people don't know what to say when the transformation is significant - not because they don't notice, but because everything they could say feels loaded. The shared Reta journey with your daughter works from the opposite direction: a reference point that makes the topic easier for both of you. You can't make your sister acknowledge something she's chosen not to notice. The question is whether her silence matters enough to name directly.