Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
It is impossible for me, or anyone, to tell whether or not you would have had your attack had
rebif been started earlier. Rebif, and other injectable MS medications (the interferons), reduce risk of relapse significantly, but not by 100%, meaning that even if someone is on a medication, they could still have a relapse, but their relapse risk is just less on the interferons. In general, it is important to be on some sort of disease-modifying agent (the interferons) to continue to reduce this risk of relapse. In the next year, some new oral medications will hopefully become available for MS.
Continued followup with your neurologist for discussion of MS treatment options is recommended.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.