Hello!  
 
I think this falls in the "good problem to have" category.  I think it's actually a really great thing that your daughter communicates with you like this.  It shows that she trusts and loves you and that she wants to share her life with you.  If she feels comfortable with you now, she'll be more likely to continue to come to you with her thoughts, feelings, struggles, and relationship issues as she gets older.  I'd pat yourself on the back for what you've done with her so far and keep doing what you're doing to keep her so close to you!

May be she is watching too much TV or grown up movies. Tell her that is normal for grown ups but for kids no. That she has other things to do with her feelings like taking care of dog or car or do her home chores. Tell her rigth now it's time for you to study that year will come in the future when she grows up to have a boyfriend but right now is not the time for her. Put her samples like there is time for everything like tress first give flowers and then the fruit something like that. Try to full fill her mind with other things like  pet or gymnastics etc.

It is time to see a psychologist. If she is getting physical at age 8, that is not appropriate-2nd graders may think about kissing a boy but rarely would  be getting physical. How old is the boy? There may be some harrassment taking place that needs to be stopped, or abuse.
 
Explain that we don't kiss or touch others at this age and to just be friends. Again, talk with a doctor and the teacher to get more input. THis could be a serious situation.

You may want to read on this topic. Some kids have crushes very early in life. She may want to know more about this kind of thing. However, I would like to say be a little cautious. I would try to investigate the "kissing" incident. While I feel it may be perfectly innocent, you may want to follow up with the teacher. I would not want a boy kissing my child at school. This is inappropriate in many ways. But there is a good way to handle it without embarrassing the two children. Also, a lot of children watch movies and TV unsupervised in this day in time. It could be learned from that and this is what I would try to find out. Good luck ;)