"Yes, isn't it so.."

Her voice trails off. Della seemed nice, so Madoka wouldn't want to say anything about her that could be even slightly seen as mean! So she's not entirely sure how to word this, but she's.. she's trying..

"S-So amazing that she's so strong? Even though the situation sounds kind of scary at at the same time! I don't think I'd have any idea what to do if I was stuck on the moon for over ten years!" You know.

Just casually dropping that information.