If you rig her with traditional sphere rigging with JCM's in Poser she will work in Poser and Studio, 

To get her into a game engine, export her as FBX and just import her into the game engine. If the engine requires triangles most will do that for you automatically when reading the winding order.

If it is already low poly count figure I would not worry about poly count unless it goes over 64k when triangulated. Some engines only support 64k per wire frame and if it goes over that it is split into two wire frames.

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