Arman,
This typically happens A LOT. That is why many magicians will have items for sale after a show (not bday parties) but other events that may take place in a gym, outdoor venue, etc. Things that are easy for kids to use like the plastic ball and vase, rising wand, mini plastic zig zag ropes, etc. are big sellers for small children. It is a great way for you to make some extra cash as well.
Now in your instance this girl is 10 so I'm assuming that she is in 4th grade. I have no idea if the set I am linking below is good or not but here is what is important. The minute the child finds 2 or 3 items out of a kit that he or she can perform with and get positive reactions...they will be hooked....and hence bitten by the magic bug.
One thing to consider for youngsters whose parents want to buy them a little kit is to look for one that comes with an accompanying DVD. Most parents (sadly) won't take the time to sit with their child and help them learn and effect and within 2 weeks the magic kit is sitting in the corner of the room with other junk.
http://www.murphysmagic.com/Product.aspx?id=50022
http://www.fatbraintoys.com/toy_com.../deluxe_100_trick_magic_suitcase_with_dvd.cfm
I'll also check with one of the guys in my club who used to own a magic shop what kits he typically sold to young children.
