Many things had happened in that short moment.
First of all, Vivian came in very quietly but was still found by these snake folk. Snake folks had the gift of [Snake Sense], and their average attributes were higher than those of ordinary humans. They were a gifted race, but their growth rates were slower. Their life span was also comparable to that of the Elves.
Vivian was frightened by their appearance, thus she turned around and ran away. Unfortunately, they still caught up with her.
Vivian had no battle experience. Although Gloria had taught her a lot, the little girl still panicked a little and subconsciously used her best spells.
Level one Arcane Missile!
This was a very good low-level spell; it doesn't have a long cast time and was pretty powerful.