This is a real problem as you must not seem to 'targetting' this particular individual if there is no proper procedures in place.
It makes sense to have proper procedures in place for reporting sick from home, and leaving early due to sickness.
If you don't have such procedures it will be difficult to discipline her.
Sadly, any measures will impact on ALL staff and should be managed properly, and it is going to take time.
The advice given here is very good, and following it (or an adaptation to suit your own company requirements) will protect you if you need to discipline this employee.
http://www.practical-hr.co.uk/index.php?page=a bsencemanagement&PHPSESSID=4e7c080fda72213fec7 e47b2563b8bd9
Good luck!