boelenis need to keep in special climatic conditions, in this case to increase the heat is not a good idea. With good feeding schedule and good husbandry, she'll get the size. With 4 years she just a teenager.
/But now I'm sad a little bit.. I love Boelens, and I collected as many informations what I could, and visited the closest people who keeping them to learn everything before I get one. In that topic the question is: Will my boeleni female growing up to X size? Most of the people who answered don't have an idea about that snake and don't gave the proper answer for the question (Respect for the exception). And what I see I go against the mass, cause people like that answers. Everyones problem that the OP wanted that snake for get the size what he like. We're in the same shoes.. We keep different ball morphs because we like their look. We keep reptiles because they're beautiful and interesting in our way, not because they bring back the ball if we throw./