The night that the royal family came to visit the Valley of the Living Rock, Bulda was in her rock form, enabling eight-year-old Kristoff and Sven to stay hidden from sight. She soon revealed herself and hushed the two so that she could listen to Pabbie speak to Agnarr; however, she took a liking to the two "cuties" after Sven licked her and decided to adopt them. Over the next thirteen years, she and the other trolls cared for Kristoff and Sven.
During Elsa's winter, Bulda was incredibly pleased when Kristoff returned home, enthusiastically greeting the ice harvester and offering to wash his clothes. She grew more excited upon seeing Anna, and after inspecting her, she declared the princess to be a perfect match for Kristoff. Bulda and the other trolls tried to set up Anna and Kristoff, but the wedding ceremony was interrupted by Anna fainting. When Pabbie stated that Anna's frozen heart could only be thawed by an "act of true love", Bulda suggested that she try a "true love's kiss", prompting Kristoff to take Anna to Arendelle.
Bulda is an outgoing troll, possessing high spirits and approaching situations with an open mind. She has a maternal, caring side, having taken in Kristoff and Sven. Bulda also eagerly welcomed Kristoff "home", offered to wash his clothes, and even tried setting him up with Anna, who she saw as the perfect girl for him.
After Pabbie revealed that Anna's life was in danger, Bulda proved herself an optimist. Despite the severity of the situation, she was quick to brighten up and offer a solution in the form of a true love's kiss.
As with the other trolls, Bulda can curl into a ball, taking on the appearance of a rock. She can also roll about in this form for transportation.
- Bulda is seven hundred years old.
- In some printed media, Bulda's name is misspelled as "Hulda".
- Bulda's name is phonetically similar to the word "boulder".