LaMar, 15, disappeared after she left for school on the morning of March 16, prompting an extensive search of the area. Sheriff's investigators have said they believe her disappearance is an abduction.
Marlene LaMar called Sierra her "miracle baby" because she was conceived at an age when doctors said it would be difficult to get pregnant.
"A child develops ideas of their own," Marlene LaMar said in the statement. "Sometimes a mother might disagree because of personal experiences and wisdom. We hover, discipline and teach them to be responsible. We do these things because of unconditional love for our children!"
LaMar said, "I knew she was going to be strong willed the moment the doctor saw on the ultrasound that she was doing somersaults in utero."
She added, "I love you Danielle and Sierra and I'm so proud to be your mom."
Santa Clara County sheriff's personnel are searching open fields and construction sites in south Morgan Hill today in a continuing search for the missing teen, officials said.
Teams will also search Almaden Quicksilver and Guadalupe reservoirs using a water-borne detection K-9 and sonar, according to sheriff's Sgt. Jose Cardoza.
Early in the search, investigators located items belonging to LaMar, including her bag and some clothing, but the weeks since then have produced few new leads.
On Tuesday, however, investigators said they located a red Volkswagen Jetta they believe may be linked to her disappearance. Cardoza called the development "pretty significant" and said investigators knew who the car's owner is, but did not name any persons of interest.
Cardoza also said on Tuesday that investigators are maintaining hope for a positive outcome in the case.
"We still do believe she's alive. We don't have any evidence leading us in the direction that she's no longer alive," Cardoza said.
The sheriff's office had received more than 2,000 tips in the case as of today, Cardoza said.
Anyone with information is asked to contact sheriff's investigators at (408) 808-4500 or call the anonymous tip line at (408) 808-4431.
