In this case, I would choose a 135 mm f1.8 with a fast autofocus system. I shoot static portraits and dogs in motion, so I need a versatile lens.
A 135 to 200mm lens is ideal for dynamics, but anything closer to 200 requires a pretty long distance to the model. It's inconvenient if you're shooting a static portrait and don't like to shout out loud 😊 so 135mm is optimal for me.
Another popular choice is the 70-200 2.8. Personally, I wouldn't buy this lens as the only lens because, at focal lengths around 70-150 with an aperture of f2.8, it won't blur the background as much as the 135 f1.8. If you like voluminous static portraits, you have to use it with a focal length of around 200, and that's a long way off from a model.
Consider this option if that doesn't bother you and you have something to shoot at settings like the 70 f2.8.