I just provided my employer with my maternity leave notice 2 months before I am taking it. She told me that when I return to work after my 6 weeks she will have a job for me, but it may not be the same position or shift. Is this legal?

What kind of leave are you taking? Are you eligible for FMLA? See http://www.dol.gov/dol/allcfr/ESA/Title_29/Part_825/29CFR825.110.htm for eligibility requirements.

i believe i am eligible; my company employs about 88 people and i have worked for the co. full time for the last two years.

If you qualify for FMLA, when you return to work your employer must allow you to return either to the same position or to a position equal in pay, benefits & other terms & conditions of employment.

Unless the changes would have occurred regardless of whether you took leave or not.