I hope that you are feeling all better now!My grandparents wouldn't teach their children or grandchildren French, either.I learned in school, so now they have to be careful when they tell dirty jokes in front of me ;)
I found your grandmother in the Social Security Death Index.
Blanche Ingram, born 24 Apr 1890, died Aug 1973.Last Residence: New Orleans, Orleans, Louisiana.Social Security Number Issued in Louisiana (Before 1951).SSN 433-07-7778
You can order her Social Security Application from the government for a fee.She would have filled this out herself.It should list her parents' names and her birthplace.With her full death date, you can also order her death certificate.This was filled out by someone else (her husband, one of her children), and should also list her parents' names and her birthplace.
I checked the New Orleans Marriage Index, and found the following:
Louis Mitchell, age 27, married Blanche Charles, age 20, on 11 Mar 1907 in New Orleans. Volume: 28 Page: 882
Could this be your family in 1920?
1920 U.S. Census • Louisiana • Orleans • New Orleans • ED# 80 Page 15A
1224 St. Charles St
Louis Mitchell, head, rents, black, 37, married, reads, writes, he and parents b LA, slater (house)
Blache, wife, black, 28, married, cannot read or write, she and parents b La, washwoman for private family
George, son, black, 6, attends school, b LA
And this was the closest I found in the 1930 census:
This looks like it might be your grandmother in the 1930 census (do you know if she had a daughter named Jane?):
1930 United States Federal Census > Louisiana > Orleans > New Orleans > District 186 > Page 5A
1410 Third Street (appears to be an apartment building)
Dwelling 28/Family 69 (rents for $15/month)
Blanche Mitchell, head, white, 42, widowed, age 16 at first marriage, reads, writes, she and parents b LA
Jane, daughter, white, 18, single, reads, writes, b LA, father b Georgia, mother b LA, student at school