I think... it’s a mixture of her thing not to get caught up in her emotions that are starting to brew for him but also because she mistook what the gift was for.
Something like, he was giving her something expensive since she preformed her duties well, aka he thinks she wants to be rewarded with Jewell’s. I don’t know for certain, I also thought it was a pretty strong reaction but maybe she felt she was being accused of being superficial, or just didn’t want him to think that she was
I don't think she was upset by the gift but rather maybe she noticed the expression of the duke when she requested a warm smile. It looked like it was a burden for him and that he doesn't want to and maybe she thought it's because of her, that they weren't as close as she thought they are. ┑(￣Д ￣)┍
She didn't even think that that was how he was raised. （￣へ￣）
So...she got upset over......a gift? I'm lost. Even if it was expensive u can't be that upset by it......