The 29-year-old former cast member from "The Bachelor" and "Bachelor Pad" hanged herself last week in New Orleans.
Allemand's boyfriend, NBA player Ryan Anderson, entered the church with Allemand's family, as pallbearers carried Giamand's casket.
Anderson sat in the front row with Allemand's mother, Donna Micheletti, while the TV personality's father, Eugene Allemand, wept quietly in the back of the church, People.com said.
One unidentified woman who said she had been Allemand's best friend "since we were 3 years old" told mourners: "Gia didn't have everything. She gave everything. It's hard to imagine someone with so much to give would want to take it all away."