How to react to a student who provides very critical comments about your teaching in a student evaluation survey?
You said,


  this sudden unfair comparison has gone on my nerve


It sounds like this negative feedback has provoked some strong emotion in you, and understandably so. 

But asking for an explanation is not likely to be helpful at this point. This isn't a constructive comment that can potentially lead you to improve your teaching - it's just an insult. Students take out all kinds of frustration in their teaching evaluations. If you ask a frustrated student to explain a comment they made (most likely) out of frustration, you are unlikely to gain anything constructive. The most likely outcome is that she'll unload more frustration on you.

The best reaction to this kind of feedback (assuming it's an isolated incident, and the rest of your feedback was reasonable) is to re-read the positive feedback you've received, remind yourself that you're a dedicated teacher who works hard to help your students, and put the non-constructive feedback out of your mind.

If this is an isolated incident, I wouldn't worry about its effect on your ranking within your institution. All instructors will occasionally receive some negative reviews, no matter how good they are at teaching.