Delfino next took a recurring role on the similarly short-lived sitcom "Katie Joplin", aired on The WB in 1999. The network would host her breakthrough role later that year, portraying a straight-talking, levelheaded waitress and high school student on the sci-fi teen drama "Roswell". As Maria, Delfino played one of the more realistic and relatable characters on the program, at once skeptical of and alarmed by the admission of her best friend best friend Liz (Shiri Appleby) that the childhood friend who miraculously healed her gunshot wound is one of a trio of aliens who survived a 1947 UFO crash, living among the residents of Roswell, New Mexico in human form. The actress returned to the big screen with a role as Natalie, the sensitive and awkward star of the independent coming-of-age feature "The Secret Life of Girls", a 1999 comedy-drama co-starring Linda Hamilton and Eugene Levy as Natalie's parents, a dissatisfied hippie and a college professor dallying with students, respectively. That same year, Delfino also appeared in the festival screened drama "The Learning Curve" before landing a supporting role alongside Tiffani Thiessen and Coolio in Rhino Films entry into the horror spoof genre, "Shriek If You Know What I Did Last Friday the 13th" (USA Network, 2000) and a cameo in the acclaimed "Traffic" (also 2000).