At his son's inauguration as US President, which mother was asked if she was proud of her son? and her reply was......"which one"?

At a guess, because it sounds the kind of thing she'd say, and with good reason, the mother of J F Kennedy.[Even if she did change sex,his going from 'his son' to 'her son' during the ceremony. I never knew that]

Nope Fred . Try again

If I recall correctly, it was Jimmy Carter's mother, a most outspoken woman.

More on Jimmy's mom -

She once remarked :When I look at my four children sometimes I say to myself, Lillian, you should have stayed a virgin. (Wikipedia)

When son Billy Carter's beer business had its ribbon cutting ceremony, a friend questioned Miss Lillian on whether or not she would attend. She remarked: "I attended Jimmy's inauguration didn't I?" (Wikipedia)

In 1966, at the age of 68, Carter applied for the Peace Corps. After completing a psychiatric evaluation, she received three months of training and was sent to India where she worked at the Godrej Colony 30 miles (48 km) from Mumbai where she worked for 21 months including with lepers. Emory University established the Lillian Carter Center for International Nursing in honor of the work she did in India. (Wikipedia)

On an biennial basis, the Peace Corps recognizes an outstanding senior RPCV who demonstrates a commitment to the Peace Corps' third goal. The Lillian Carter Award is in memory of Miss Lillian Carter, who served in the Peace Corps as a senior in the 1960s. (http://www.peacecorps.gov/index.cfm?shell=resources.former.staycon.lilliancarter)

Lillian Carter was born Lillian Gordy in a small town a few miles west of Plains. Miss Lillian, as she was affectionately titled by Americans during the Carter Administration, broke the barriers of segregation in her husband's home town of Plains, practicing nursing in the poor black area of town. Her son, Jimmy Carter, would later credit her with setting a "moral example" for him in her actions. (http://ourgeorgiahistory.com/ogh/Lillian_Carter)

Yes DG it was Lillian Carter. look here

I have a six pack, unopened, of "Billy Beer";
I thought it might be worth something, someday; Perhaps I should put it on E-Bay and donate the proceeds to Answerpool!