The whole sentence is in the past, but then the verb "follows" is in the simple present tense. The problem with that is it does not match the second conditional established by the modal "would", which indicates a past action. If we were to use "follows", than we would have to use "will", making the sentence a first conditional. Take a look at the sentences below to see the difference:
- She will recover quickly if she follows the doctor's advice. (first conditional)
- She would recover quickly if she followed the doctor's advice. (second conditional)
