The pair, who costarred as teenagers on TV's Sister, Sister, have spent hours planning for the April 20 nuptials.
"Tamera has been so supportive during this time because she knows things can get overwhelming for me," Tia, 29, who now costars on CW's The Game, tells PEOPLE. "From planning and throwing the shower, to coming to my dress fittings, she has been by my side."
Mowry's bridal shower was an intimate party for a dozen family members and friends at the Whiskey Blue in Los Angeles on March 14. Tia's favorite colors, pink and purple, were everywhere – from the pink champagne to the purple orchids. The menu included her favorite foods: pizza and sushi.
Tia's Game colleagues, Wendy Raquel Robinson and Brittany Daniel, have helped Tia celebrate her upcoming nuptials both off and on the set. "Today at work, she was screaming at the top of her lungs. She was so excited," Daniel said.
At the shower, Tamera presented her sister with a homemade scrapbook – complete with photos and invitations – documenting everything throughout the engagement. Said Tia: "There's nobody in the world that knows me better than my sister."