Photos and VideosMore Photos and Videos
The 25-year old is married to Fall Out Boy bassist Pete Wentz, who was also at the show.
Ashley Simpson-Wentz made her Broadway debut last night and ever-supportive sister Jess said her younger sibling gave a stand-up performance.
Jessica showed up at New York's Ambassador Theater in a silver-scaled sequined gown to cheer on Ashley, who played Roxie Hart and appeared on stage with dark hair, pale skin and a svelte figure.
"Roxie was all Heart! Watching her up on that grandiose stage made me the proudest sister in the world. I love ya honey, I love ya!" Jess wrote on her Twitter page after the show.
The protective older sister took "Melrose Place" to task after the TV series dropped Ashlee from the lineup.