Final answer:
The sentence in question is a simple sentence because it has one independent clause, one subject, and conveys a complete thought.
Step-by-step explanation:
The sentence "Ever since the big blowout, she and I haven't gotten along" is an example of a simple sentence. A simple sentence contains one independent clause and expresses a complete thought. Despite the presence of a conjunction 'and', the sentence still only has one subject ('she and I') and one verb ('haven't gotten along'), which makes it simple.