Best strings for a 13 year old

[NelloSanti]

I need your advice gentlemen

After having ordered a set of Flexocor '92 for my daughter, I spotted Calvin's posting about getting a free set from pirastro, I decided to try it myself (can't hurt can it?). Well they emailed me back to say that they would send me a free set. I prceded to cancel my order and eagarly awaited for the free set. They finally arrived yesterday and I now have two sets the first is Felxocor G, D, A with a Permanent E (this spec adviced by Pirastro themselves) and the other is afull set of Evah Pirazzi. My dilemma now is what should I put on first? I have read great things about the Evahs but also know that the Flexocor seem to be the orchestral "standard" (here in the uk anyway).
What do all you experts suggest would be best to try first for a 13 year old girl, she plays a 1950s fully carved 3/4 Checkz made bass, and got a place at the Guildhall School of Music in London starting from September.
Please forgive me if this seems a stupid question but I am quite new to Double Bass and would welcome all comments.


Thank you
Nello