Take a look at the original sentence again:
Ursula clutched her head, trying to remember the correct formula to solve
the statistics problem, the only thing she
could focus on, however, was the stupid fight she had in the car with her
boyfriend, Mac.
You wanted to fix it this way:
Ursula clutched her head, trying to remember the correct formula to solve
the statistics problem, consequently, the
only thing she could focus on, however, was the stupid fight she had in
the car with her boyfriend, Mac.
A comma splice occurs whenever you join two complete sentences with a comma alone. Ursula clutched her head ... begins one complete sentence. The only thing she could focus on, however, was the stupid fight ... starts a second complete sentence. Just because you add a transition like consequently doesn't mean that a wimpy comma can now correctly connect two complete sentences.
You might want to consult the rules for fixing comma splices and fused sentences.
Go back to the sentence to try again.