It depends. If it's pregnancy medicaid only then no it will not cover anything that does not have to do with your pregnancy. If it's regular/full medicaid then yes it should cover your eye glasses and exam. I received full medicaid for my pregnancy, and yes it did cover my eye exam (my vision has become worse during pregnancy so I did need to update my prescription.) In some cases, pregnant women are only given medicaid to cover their pregnancy related appointments. Just have your girlfriend go to a local eye doctor. She can show them her insurance card and they will run the number and tell her whether or not her medicaid is full medicaid.
As I know that pregnant women of any age who are eligible through the pregnant women program are only eligible for pregnancy-related services. If the PW participant has a vision problem that has been caused by or is exacerbated by the pregnancy, then the eye exam and treatment are covered. Routine eye exams, eyeglasses, and contact lenses are not covered for women on the PW program.
It is important to understand the specifics of your Medicaid plan and reasons why you may not be eligible for a particular service. If your Medicaid plan does cover the costs of vision care, there may be additional stipulations regarding the extent of the eye exam, what type of eyewear can be purchased and the frequency of the exams. Consult your Medicaid agency for your coverage details.