The 55-year-old, from Paisley, who has relapsing remitting MS, was initially being treated with disease modifying drugs through injections. However, this did not produce the hoped-for improvements to her condition.
She accepted an offer of a chemotherapy treatment, which can be given to patients if usual treatments have failed. Since then, she has seen her health improve drastically, having one relapse in four years.
Ms Stirling, who probably had MS for more than a decade before being diagnosed, welcomed the approval of alemtuzumab, which, as with chemotherapy, was originally a cancer treatment.
She said: "Everyone is an individual and what works for one person, might not work for the next, so to have a new drug is fantastic. I think people should know about these treatments, and at least have the option of trying them out. This is a positive step.
"I wasn't good before. When I decided to have chemotherapy, everyone asked me what I was doing, but the injections weren't working for me and my neurologist had suggested it.
"Now my life is going very well - I've got my health and I'm happy. At this moment in time, I'm feeling very positive, but if I wasn't I would try anything."
Describing relapses, which alemtuzumab has been shown to reduce, she added: "If you were 100 per cent fit, you will come back but you might only get to 95 per cent of where you were. The next time you get back to 90 per cent, so it's a slow deterioration. If this offers hope for others, then bring it on."