My student's son had measles.my student came to class for 1 day&then stopped coming.can she give the measles virus to other people if she was infected?

Yes: If she were infected, she will give her measles to other people who are not immune to measles. If she were infected, she should have no contact with vulnerable people until the health department staff say it is say to do so. The health department can track her contacts and do blood tests to see who is immune to measles. Normal, healthy people who are immune (by blood test results) should be fine.