>>90676990>>90677216It all comes down to Star's mother.
(This sounds like I'm joking but I'm being at least half-serious.)
Moon raised Star, the future queen, with sky-high standards. Anything Star did could be done better; nothing she did was ever good enough. By this, she meant to goad Star into excellence, but instead Star ended up with a complex over being a failure, incapable, a disappointment. It's how she sees herself, but it bothers her like nothing else (except for Marco being with another girl.) Whenever someone else says or implies she's not good enough or not capable (Marco trying to rescue her from the Blood Moon Ball, Ms. Skullnick giving her an "F-" in "Match Maker", and yes, Marco admitting he didn't think she could handle a day out on her own in "The Banagic Incident,") she's driven bonkers.
Now, she describes herself this way, too, usually in overdramatic form: "Starred it up" in "Pixtopia", the whole "Royal Shame" sequence in "Face the Music". I think she's hoping for someone to tell her she's wrong - she loved it when Marco took equal responsibility for her attack on the football game in "School Spirit" - but they usually don't!
Moon realized, from hearing the story of Ludo from his parents, that overly harsh parenting could cause the downfall of a house (literally, in the case of the Avarius family: kaboom!) So when she next saw Star, she made sure to show her affection and tell her she was proud of her. But, uh, in the famous words of Love Sentence, that was Too Little, Too Late, Moon: your daughter already sees herself as a gigantic failure and is about to introduce herself to the kingdom in that way! Great management of your dynasty!
(Half-serious, remember. I do think I'm reading at least a BIT too much into all this, see.)