Okay - so I don't know about you - but I have a pretty good recollection of my youth in elementary school days. How often did you feel sexually aroused by any gender, or any topic of conversation? None? Oh yeah, because it's literally impossible to feel something that you do not yet understand. You don't even have the hormones that would allow for such a thing to declare. There are no "signs", what you're referring to is just mistaken for attention whoring. It's okay for you to stand up and say "I don't know what my child is feeling or doing" when it comes to a topic. You don't need to take them to a psychologist or declare that they are a female in a male body - it's simply the process of growing up.
I'd say a majority of kids develop crushes at a very young age, and it's almost certain to be directed to the gender of sexual preference.
I still remember my 1st grade teacher as a very cute lady, and my mom still laughs at the fact that when that teacher announced her impending wedding I had a huge tantrum and melt-down, both at school and later at home. In 2nd grade I was also part of group of 6 boys sent to the Principal, caught cutting out boob pictures from some Hollywood gossip magazine. I daresay if at that age (6? 7?) I had a crush for a male teacher, or accumulated penis pictures, it would have been noticed; and also, if that led to reprimands or punishments, a kid would remember to hide it or be miserable.
Nothing unusual for an 8 year old to understand what her heart wants.