Silver Sequin Evening Gown

Ever Pretty size 20, silver all sequin evening gown. never worn, still have packaging, but no tags as this was bought online. Very stretchy & comfortable, fairly low-cut. Purchased by my sister in law, but it was too small for her & too big for me (as you can see). In photos I'm 5'2" & 160lbs and as you can see it is much too large. My sister-in-law is approx same height as me, but normally wears a size 20, this dress was much too small for her, so I would say normal size 14 or16 should fit.