Could you help me clearing this doubt?

I had the following sentence to rewrite as an If-clause:;

- Mary spent many years studying English, so she speaks English fluently.
I rewrote it like that:
- If Mary hadn´t spent so many years studying English, she wouldn't speak English fluently.
It seemed to me that this would be the logical way to rephrase but a friend of mine insists on the use of the Past Simple in the If-clause.

My doubt is if I could rewrite it like: If I didn't spend so many years studying english, I wouldn't speak English fluently.