Way too many factors to consider here...such as:
1. Genetics (the biggest one)
a) is she arleady somewhat in shape?
b) how does she gain naturally?
c) You have consider she needs time to "cut up" as well as build muscle
2. Obviously Training/Diet
3. Supplements/Gear if any
4 Months would be impossible for a BB'ing competition, however I'm not sure what exactly is required for a figure comp. Like I said, if she has great genetics already then I would say it's possible, but if were talking someone who's chubby and hasn't worked out very much in their life then I would say wait for the next comp.
