I don't think the item in question has anything at all to do with Nailsea, either in style of the item, or in decorative concept :!:
It looks to me like a late 19th century piece and could be English or "Continental Europe". The shape of the top does bring "Hatpin holder" to mind, but yes, it could equally be a flower holder. In Victorian Decorative Glass (2002), by Mervyn Gulliver, page 100 has a picture of a 6 inch high vase with a similar "crown" top formed in loops of plain green glass. Unfortunately, attributions are not a normal feature of what in other respects is an excellent book.