It’s been very smart of her to wait. Very, very smart. For so many reasons. Saved on wasteful campaign expenditures, allowed other candidates to be vetted, and avoided the unbalanced media dynamic that would have formed around her to the detriment of the race. But, it is now getting to be crunch time... We’ll need to hear in the next week or two.
My bet is she's put a LOT more thought into this than you have.
She is still far more of a known quantity than any of the other GOP candidates. There is no need for her to get in until the very last minute. By waiting she lets them receive a small measure of the anal exam she has already been subjected to.
She's known for a long time when she is going to pull the trigger.
That will be quite obvious when the time comes.