She is either in 4th or 5th grade which this I am assuming. This would be an age at which there could be some hormone changes, which would correlate with the crying. However, you may want to find out what else could be causing the emotional breakdowns. And this is what is going on, it is a "breakdown" of sorts. Think of yourself, what causes you to cry and get upset? It could be stress, hormones, certain kids, a teacher, or perhaps a combination of all of this. The best thing to do is to have an open conversation with her while she is not upset or emotional. You are a sense of comfort for her and this is why she misses you, but it could be something else that is triggering this.
Another thing, is hormones can do some really tricky things to us as girls/women. I would also find her a good doctor and discuss options if it continues. Also, look very closely as your daughter's diet. Some foods can aggravate the symptoms of anxiety and maybe even depression. You may want to go gluten free and put more fruits and veggies as a snack into her diet. Also, a multi-vitamin is a good suggestion. Below is a link to the gummy vitamins that we use. Good luck!

Definitely checking out what is going on at school that might contribute to your daughter's being upset is a good idea.  However, consider the possibility of your daughter worrying about what might be going on at home when she is at school.  Have there been any changes in your family dynamics or your health?  She either misses you while in school because she is upset by what is going on there, or she is worrying about you.  If you already talked with your child and her teachers and you did not find a solution, consider talking with your daughter's health care provider.  

Best regards.

My daughter now 14 came home from 7th grade on Oct 29 and told me she was not going to school again. I contacted her pediatrician who told me to take her to the hospital for a psychological evaluation. Long story short she spent a week at Sheppard Pratt Day School where she goes from 9-3 to be observed and evaluated. She was diagnosed with severe anxiety disorder and depression. She was given medication and started therapy sessions. She is now in high school and getting good grades and continues to take meds and therapy. Hope this helps and Good Luck!!!