Miss Selfridge vintage never worn black with pearl collar mini dress small or xs

Miss selfridge dress bought overseas. Tag says size 8, but fits like a 2 or 4. Dress is 2 pcs. Slip has adjustable straps and is light pink, slip is tight across breast with very little stretch. Bottom has ruffled slip. Ties in back. Saved for daughter but may never wear. Never worn because so small. Zips on side. I am 5’7” and 32C and slip is tight over chest. Would make a cool RBG or a cute Wednesday costume.