Alegría began her acting debut in the TVN soap opera Borrón y cuenta nueva in 1998, playing the role of "Doris Morán", a religious nun who was rethinking her life after she found a new lover.
In 2004, she left for Canal 13 to participate in the soap opera Hippie and also Tentación. Not happy with her contract to Canal 13, she decided to return to TVN.