Wait. It's the best you can do now.
She's most probably not over her crush yet, let alone ready to appreciate you as a boyfriend. And you will have a lot more chances at a serious thing between you two if you give her time.
If you tell her now and she tells you she likes you too, you can't trust those words. She could just want, for example spite he guys who rejected her. You don't want her to use you.
"But I, being poor, have only my dreams;
I have spread my dreams under your feet,
Tread softly because you tread on my dreams"
- WB Yeats