The second most emotional day, she said, came Monday.
In the afternoon, she planned to see off her younger son, Jake, who was scheduled to leave Monday evening for Marine Corps boot camp at Parris Island, S.C.
In between, she said she was "emotional, very emotional. … Although I'm going to put on my face when I go home for Jake, let him know that I'm proud of him and I want to be strong for him."
Hundreds of family members, friends and admirers gathered at Dulaney Valley for the 90-minute service to honor Marylanders killed in Afghanistan since last Memorial Day.
Honored were Marine Corps Sgt. Julian C. Chase, 22, of Edgewater; Navy Special Warfare Operator 1st Class Patrick D. Feeks, 28, of Edgewater; Army Capt. Sara M. Knutson-Cullen, 27, of Eldersburg; Mills, 21, of Laurel; Army Staff Sgt. Brandon R. Pepper, 28, of Baltimore; Army Staff Sgt. Daniel A. Rodriguez, 28, of Baltimore; and Army Sgt. David V. Williams, 24, of Frederick.
"This holiday is more than a three-day weekend. It's more than weekend sales at the mall or the auto dealership," said Col. Linda L. Singh, director of the joint staff of the Maryland National Guard. "It's meant to honor those Americans of many generations — and we see many generations before us — who put on the uniform of our country's armed forces, went into harm's way, and did not come back.
"Whether you agree with our participation in the current conflict in Afghanistan and other hot spots around the world, the hard reality is that America's best and brightest are shouldering burdens that others can't or won't."
Other service members with Maryland ties killed in the past year include Navy Lt. j.g. Valerie Cappelaere Delaney, 26, a Naval Academy graduate from Ellicott City, who died in March when the jet she was piloting crashed outside Spokane, Wash.; and Marine Lance Cpl. William Taylor Wild IV, 21, of Severna Park, who died in March during a training exercise at Hawthorne Army Depot, Nev.
Navy Diver 1st Class James Reyher, 28, and Diver 2nd Class Ryan Harris, 23, died in February during a training exercise at the Underwater Explosion Test Facility, known as the Super Pond, at Aberdeen Proving Ground.
Their deaths came weeks after the death in January of George H. Lazzaro Jr., 41, of Nottingham, a former Marine working as a civilian engineering technician, during routine maintenance at the Super Pond.
One of Eugene Mills' grandfathers served in the Army; the other served in the Navy. On Memorial Day, his mother said, he would call them each to thank them for their service.
When he watched the Twin Towers come down on Sept. 11, 2001, his mother said, he decided he would serve himself. He was 10 years old.
"He wanted to go over there and fight for freedom," Theresa Mills said.
She remembered her son as "a jokester."
"He cared about everybody and he had a great sense of humor," she said. "Very outgoing and just a great kid."
Former Marine Cpl. Tim Nelson went to the Marine Corps School of Infantry with Mills, served with him at Naval Submarine Base Kings Bay, Ga., and deployed with him with the 1st Battalion, 8th Marines. He was on an operation with Mills last June when he heard small-arms fire and watched the medevac helicopter come for his friend.
On Monday, Nelson joined Theresa Mills at Dulaney Valley.
"It's true that you lose the best," said Nelson, of Baltimore. "Geno, that was the best Marine I can honestly say I've ever known. Just the way he carried himself, the way he cared about the Marines that he was in charge of."
He also remembered Mills' lighter side. As in the night he and a confederate crept up on a Marine standing watch, tossed a dummy grenade into the post, and videotaped him as he dove for cover.
"It sounds cruel to anyone who doesn't understand," Nelson said. "That's how Marines act. … It was hilarious."
Communities across the United States remembered the nation's war dead Monday in ceremonies at cemeteries, memorials and monuments.
"Captain Sara Cullen had a smile that could light up a room and a love of country that led her to West Point," Obama said. "And after graduation, Sara became a Black Hawk pilot — and married a former Black Hawk pilot.
"She was just 27 years old when she and four other soldiers were killed in a helicopter crash during a training mission near Kandahar. This past April, Sara was laid to rest here, in Section 60."
Obama then named others interred at Arlington, and concluded: "Today, we remember their service. Today, just steps from where these brave Americans lie in eternal peace, we declare, as a proud and grateful nation, that their sacrifice will never be forgotten."
Service members with Maryland ties who have died in action or training since Memorial Day 2012:
Marine Sgt. Julian C. Chase, Edgewater; Afghanistan, May 28, 2012
Marine Lance Cpl. Eugene C. Mills III, Laurel; Afghanistan, June 22, 2012
Army Staff Sgt. Daniel A. Rodriguez, Baltimore; Afghanistan, July 18, 2012
Army Staff Sgt. Brandon R. Pepper, Baltimore; Afghanistan, July 21, 2012
Navy Special Warfare Operator Petty Officer 1st Class Patrick D. Feeks, Edgewater; Afghanistan, Aug. 16, 2012
Army Sgt. David V. Williams, 24, Frederick; Afghanistan, Aug. 18, 2012
Navy Diver 2nd Class Ryan Harris, 23, Gladstone, Mo.; Aberdeen Proving Ground, Feb. 26, 2013
Navy Diver 1st Class James Reyher, 28, Caldwell, Ohio; Aberdeen Proving Ground, Feb. 26, 2013
Army Capt. Sara Knutson-Cullen, 27, Eldersburg; Afghanistan, March 11, 2013
Navy Lt. j.g. Valerie Cappelaere Delaney, 26, Ellicott City; Harrington, Wash., March 11, 2013
Marine Lance Cpl. William Taylor Wild IV, 21, Severna Park; March 18, 2013
Source: Department of Defense