That sounds like a legend. She married with her first husband in 1935 when she was 18-17 years old. If we assume she came to Turkey after her marriage and if according to her word Atatürk was 56 years old at the time this means she wasn't 15 years old. Bits I found in the internet says this legend solely comes from her 1991 autobiography*. Of course this casts doubt to this even more considering how long ago the supposed relationship happened then there is the virgin wife problem and more importantly Atatürk's health. Beginning with 1937 Atatürk suffered through some serious health problems and that parts of his life is documented with detail. Why didn't anyone else commented about this later? Overall this doesn't sound plausible, maybe a wet dream recalled by a old lady. You can have a idea about what kind of "backlash" would have happened if this was real by looking at Atatürk's other relationships.

*http://www.dailymail.co.uk/news/article-4047704/Pictured-Zsa-Zsa-Gabor-hospital-bed-known-photo-legendary-star-reveals-final-years-plagued-ill-health.html, http://www.mirror.co.uk/3am/celebrity-news/zsa-zsa-gabor-dead-99-9482638