In terms of personality, Hildegard is very much like her friend Amber, in that she tends to be snobbish, self-centered, bit of a brat, and having a tendency to act aloof to those she finds beneath her, a result of being indulged too much by her father King Henrik. Hildegard is also very proud and confident in herself. Her stoic personality is what separates her from the other princesses. Usually, Hildegard will be seen wearing her haughty smile and carrying herself in a manner that tells others she's "a cut above the rest." In fact, as Zandar finds out in trying to impress her, she is only truly pleased when in the spotlight. However, that image withers away In "The Princess Test". When Hildegard feels the pressure of an important test, she tries to hide away, not wanting her friends, especially Amber, to see her in doubt. However, Amber, donning the maternal role Sofia played to support her, offers some words of encouragement and Hildegard regains her confidence, thus passing the test. Hildegard, though mostly like Amber in nature, does have some contrasts: Unlike the flamboyant Amber, Hildegard has a taste for simpler styles. She liked Sofia's small garden tea party, saying it reminded her of countryside picnics. She is also willing to try new things if only to find something to impress her. She can also be very insensitive to others, such as when she accidently hurt Sofia's feelings by telling her that King Roland was her stepfather and not her biological father in "Dads and Daughters Day".
In the episode "The Princess Stays in the Picture", Hildegard finds herself confessing to Sofia that she acts the way she does because she thought that, after embarrassing herself on the first day of school, the only way to get other people to like her was if she acted like a perfect princess with the answer to everything. Sofia told her that it was better, to be honest and humble so people can see the real Hildegard. In the end, Amber noticed that Hildegard changed and that Hildegard and Sofia are now closer as friends.
Her friendship with Clio is explored more in "Sidekick Clio". It's revealed that she won't let Clio do anything she likes unless she likes it and they do it together. It took some choice words from Amber and watching Clio on stage to realize that she had been acting very selfish. Reconciling with Clio, she agreed they could do what Clio wanted, from now on as well because they didn't have to do everything together.
She is shown to be demanding and wanting anything she sees in an instant. This is shown in "Olaf and the Tale of Miss Nettle" when she sees Olaf and asks her father for a talking snowman. This is also shown further in "Dads and Daughters Day" when she tells her father that she wants at least one animal from the Enchanted Animal Park which leads to trouble.
Hildegard has a cameo appearance in the special "Elena and the Secret of Avalor" as she speaks with Amber before leaving to return home for summer break from Royal Prep.