They first met each other a year before summer camp, when the Digitama appeared in Lara's room. It hatched into Dodomon, who Lara looked after as if Dodomon was a real baby. When Dodomon transformed into Dorimon, or 'evolved' as he later explained, Lara was taken aback by surprise.
She introduced herself and he revealed his new name, the two seeming to get along just fine. Lara subconsciously found herself opening up to Dorimon. She thought that was a good thing to have happened, since living in the shadows was not always good. Having a friend now changed her outlook.