There are many reasons that girls should not serve in Tzahal. Perhaps the best one is that the Gedolei Yisrael [such as the Chazon Ish, the Chebiner Rov, Rav Tzvi Pesach Frank and many others], said that it is nothing less than יהרג ואל יעבור.
Now that we see what the enemy does when women come into their hands we have another good reason.
Sadly, all this doesn't stop one well know rabbi from having a program for girls to study and then join the army and others rabbis from encouraging girls to enlist.
This is just another example of misguided people thinking that they are doing females a favor when it they are actually doing them a grave injustice.