I dont know..
If i were in your shoes ( im picturing school crushes as we speak) i would at least say hello.
She may not even recognize you... YOU may not recognize her either.. hehe.
But so much time has gone by that I dont think it would be rude of you to approach her in the grocery store even if she doesnt know who you are right away.
Usualy, crushes from school, dont result in an adult "crush" later on in life. Your ideas of what you want a woman to be have changed and you have changed.
you never know though.. she may end up being a great friend!
Or... a good laugh for you.. if she turns out to be a really wierd person.