You can't trademark a person's name per se, whether it's a stage name or their legal name. A name can only be trademarked when it is actually used in commerce, representing a specific "brand" of product or service. So unless the model also has a line of products or services being specifically marketed using their name as a trade name for the product/service (ie Johnson & Johnson or Bob Evans Restaurants), it is not and will not be trademarked.

You can and should use your model's stage names whenever possible. That is how the material is identified and searched for by your customers. That is also how a model makes a name for themselves in the industry.