I love this drapey sequin tee (I bought one myself recently!), and with cropped pants and some trendy wedge/heels I think Heather will look stylish yet not too revealing for a work related event. You could also pair the sequin top with a pencil skirt like this one.
If Heather feels more comfortable in a dress, this option from MICHAEL Michael Kors is both conservative and festive! I love the metallic tweed. It looks as though it's only available in petite online - they might have regular sizes in store. Click HERE to see an alternative dress.