The teen years can be a challenge for both parents and the child. However, it is up to the parent to help show guidance and clear parameters during these times.
These are few suggestions that come to my mind.
First, host a parent supervised gathering for your child, her "crush" and others. Have a fun movie night, pizza party, etc. so that your daughter can be in the company of her special friend but also under the watchful eye of her parents. Make your home THE place that kids want to hang out. Sometimes, this means stretching the budget a little for Friday night snacks. But, don't hover over the kids when they are there. Simply keep visiting their area with bowls full of popcorn all while letting them know that they are being watched from "afar".
Second, if she insists on going out be sure it is a school sponsored event or a group event with other supervised parents.
Third, let her know your rules. Such as NO double dates until 8th grade or later. And certainly read up on the basics of the tween and teen development years- such as why middle school students should not date high school students, etc. See Michele Borba's books on Parenting to help you with these areas.
In additon, there are many good books that help kids this age through the difficult years. I suggest the Middle School Confidential series by Annie Fox and the American Girl Series. Both available online and in bookstores.
Both give excellent and sound advice. They are relatable to tweens and also help as a springboard for discussion between child and parent.