Take a look at the sentence again:
In the restroom, Tishena was brushing her
hair, freshened her lip-gloss, and
took deep breaths, trying to work up the
courage to walk to her first speech class.
When you list actions, you must use parallel structure. Here, freshened and took are both simple past tense verbs, but was brushing is past progressive, wrecking the parallelism.
To fix the sentence, change was brushing to brushed.