This has always been a challenge for me also, but my situation is a little different. We race BMX together, 6yr old, 10yr old and myself. Being on the track together is a childhood dream but can be a major hurdle. I think the biggest thing to overcome is how your interaction is while racing and being Dad at the same time. You will want to focus on racing but your kids are in the back of your mind, where as before they may not even be at the event. We got to a point where we would not pit with our family members that were not racing, mainly to focus on what we were there to do. My oldest son likes it better when we are both racing, pitting, warm ups, stretches and competitor assessment together. When my youngest is racing, I am a headless chicken and focus on having fun rather than podiums.
For your situation, its gonna be different. I can see my kids, were as you can't. An option to do is to create a team atmosphere for her. If you got a friend or family member that is a cyclist, having a cyclists friend helps, they know what is on the trail. I always had my wife and other team mates for this, for you guys its one big race, between the three of us we would have up to 12-16 short ones. If she is comfortable on the bike and has fun while riding she should be fine, but if there is any pressure to start the race and uncertainty, I would wait till the time is right. You have many more chances to try it again, one bad first experience could lead to it not happening at all in the future.
I put my oldest in this position a few yrs ago. He was doing awesome on the local level side of racing, slowly gaining towards his next class. We decided to do a National race at Powder Springs. He had a good first round, won the second round. Had an awesome gate in the main event and got taken out by a dirty rider from out of state who never came to shake hands or check to see if Sean was ok. His brake noodle was smashed and folded over where the kid kicked Sean's bike. Sean sprang both wrists and have a slight concussion. I think he did three more races that season, two of them were not pretty. The third, he was fighting the fear so severe, he was loosing sleep and come race day as my kids say (vominaded). It ended that season, I was torn up pretty bad, felt like I had wanted it for my own goal and not his. He wanted to race but took him a while overcome the mental blockage it had created.
With that, if you think she is too young, listen to yourself, you know what's best and remember. Bad first race= no more desire to race or fear of racing. Waiting for the right time= a lifetime of racing together.
gotta get up to get down