My female rabbit grunts when I try to pet her?

When I go to pet my 10 month old female rabbit she starts making this grunting noise..it's not a loud or squeal-ish noise, it's very subdued and quiet. she just started doing this yesterday. she eats normally and whenever i leave she goes back to her old hoppy and perky self. is she just scared of me? i've had her since the day she was born, she was part of a litter from last may that my other rabbit had.