Sherut Leumi is not compulsory for religious girls, on the contrary, it is done on a voluntary basis.
(Or… A general noble feeling of obligation to the country etc etc etc)
In addition, if a girl were to be dissatisfied with her placement, she would be entitled and able to move to a different place to do sherut leumi, or to even pull out altogether. For this reason there are those today who see sherut leumi as a viable option for their daughters, and not as such a halachik problem as in the past, perhaps. I would however be concerned-or at least cautious- about sending my daughter to sherut leumi, but for other reasons, namely issues/dangers that exist in this area. It is not uncommon to hear of disturbing stories concerning sheut leumi too. This is aside from the spiritual and religious aspect of the story, and the dangers that such excursions pose.
Use some seichel- do not be naive about sending your children off to places of dubious standard and safety, be this sherut leumi or seminary. Yet do remember that there is a lot of good that your daughter could learn in seminary, or achieve in the world in general, and prohibiting and permitting must each come in their correct time and place.
Hatzlacha Raba