To try to help you, that "Hyuu" can probably be translated as "Sigh..." or maybe "Whew..."
According to this sound effect translation site,
http://thejadednetwork.com/sfx/search/?keyword=hyuu&submitSearch=Search+SFX&x=, it means the sound of wind blowing and with the context that she is using that sound, it is reasonable to assume that she is either sighing or just exhaling strongly to express her emotional feeling.
Back when I was working as a proofreader for Death Toll Scans and a number of other scanlation groups, I often used The Jaded Network site to translate sound effects that many translators back then didn't bother with translating. I found it to be a pretty good resource for such things.