Dorothy Braund is among those rare phenomena, an artist who becomes collectible within their own lifetime.
The problem with prolific, well-known contemporary artists whose work is climbing in value, is that there will inevitably be many copyists, imitators, and even forgers who will have replicated her paintings. With this in mind, you need to approach one of the larger auction houses if you are hoping to sell. The big international auction houses such as Sotheby's have a pool of experts that they can call on to give advice. Try emailing your inquiry in the first instance and include photos of your item from back and front as well as a close-up of the signature and details of its provenance.