@Framing A Moose -sigh- there isn't really a loop hole Moose to get your summon to always be there until your summoner is strong enough to sustain them. for various reasons besides just keeping everyone fair and balanced especially early on. Summons are beings of magical energies, and they require a constant supply of that magical energy to live. Their own worlds are full of magical energy so they don't have to worry about it, but that is not the same in the human world, any summon who completely passing over to the human world has to have a constant supply of magic in one form or another in order to live. without it they'll fade away into nothingness. this can be done various ways but none of them nice or friendly.
Plain and simple she wont be able to keep her summon in their world for long periods of time until she trains. as stated this is for many, many reasons.