Vintage jewelry

My husband's great aunt lived until 1983 and was 96 at the time that she passed away. This belonged to her.  She was the rare woman in business in NY her entire adult life and collected a lot of fine things. I have her fine jewelry identified, but I can't tell if this is just pretty costume jewelry or something of value. It has fine chains (think they are gold) connecting to make the triangle "pendant shape" that falls in front and in back where the clasp would normally be, but this is a side clasp necklace.  I'm thinking the stones are glass cut to look like diamonds but I doubt that they are actual stones. It's a very dainty piece that makes me think "flapper era." Any help in identifying what type of necklace this is or a possible period of time would be appreciated.