No, it is not likely that her cognitive numbers would come out below 115 if her achievement is that far above grade level (keeping in mind, of course, that GE's are not truly accurate measures of instructional or mastery levels--but the best you have under the circumstances). For most people, there is a reasonable level of correspondence between ability and achievement, and typically, discrepancies are in the opposite direction (ability higher than achievement), with the possible exception of rote or basic skills, which are occasionally splinter skills.
(E.g., I've had a number of students who could be considered intellectually impaired, by some standards, who were able to read and spell at an age-appropriate level, and occasionally one finds ASD learners who have similar splinter skills in decoding/encoding or mechanical calculations, but in both cases, without necessarily the accompanying high-level problem-solving or comprehension skills that one would expect in a higher-functioning learner.)
