If this is your Inez in the 1940 census:https://familysearch.org/pal:/MM9.1.1/KQ8T-36S
Then this appears to be her mother and siblings in the 1930 census:https://familysearch.org/pal:/MM9.1.1/XHS8-JRN
The birth places of her siblings and their dates of birth would indicate that Inez was probably not born in Pennsylvania. As a great grandchild you may request a search a PA birth record, but frankly I don't think you will find one. Since you are unsure of the year and don't know the county of birth, even a multi-year search may be unproductive. Here however, are the instructions if you wish to pursue a PA birth certificate:http://www.portal.health.state.pa.us/portal/server.pt/commun...
The cost for a 2-10 year search is $45.
I didn't find a record of a marriage license for Inez having been issued in Delaware County:http://w01.co.delaware.pa.us/archives/marriagearchives.asp
I also didn't find a marriage record searching Philadelphia County using Familysearch.org.