I have to admit, I assumed from your first post you meant both English. It is fairly standard to do 2 English, so I could understand someone looking at an application form and questioning why this applicant only managed one.
Deadly dull? Unlike history, right? Most subjects are 'dull' if it doesn't interest the student.
OP - computer Science is quite factual while history requires the student to examine source material and to give an opinion. If your DD has a talent for making a reasoned argument then the choice is clear.