[4] On November 12, 2021, she was acquitted by Sandiganbayan of graft and malversation charges in relation to the alleged misuse of ₱10 million in Priority Development Assistance Fund for supposed ghost projects in 2009.

Cajayon won as representative of Caloocan's 2nd district in 2007, defeating reelectionist Rep. Edgar Erice, Nilo Divina and one other candidate.

[7][8] In 2009, she was given the Award for Congressional Legislative and Service Excellence by the Consumers League of the Philippines Foundation, Inc.[9] She won a second term as congresswoman in 2010, defeating Antonio M. Almeda, Carlos Cabochan, councilor Rose Mercado and four other candidates.

[12] In September 2021, she joined the PDP-Laban party of president Duterte days before the filing of certificates of candidacy in the 2022 election.

[13][14] Cajayon-Uy ultimately won a third term as congresswoman of Caloocan's 2nd district, receiving more votes than Roberto Samson, Luis Macario "Maca" Asistio and two others.