You can actually do a good job with umbrellas, but they take extra work. The umbrellas tend to spread the light all over the place. Some bounces off the ceiling, floor, walls, etc and as a result you sometimes aren't able to develop the shadow areas of your photo. The first thing to try with the umbrellas, is place one on either side of the model at about a 45 degree angle in front of the model. Have them the same distance from the model. Now in one of them have your light at full power and on the other at 1/2 power. Keep in mind that the closer the umbrellas are to the model, the softer the shadows will be and the further away the harder. Naturally as they get closer, you'll have to stop down, or you'll have to reduce the power of each head (but keep the ration the same as above).
Now shoot shots and see what the shadows look like. If the model looks straight ahead, then the shadow the nose casts will determine your type of lighting. Shoot some with her looking at the main light. Some looking at the fill light, Then raise the lights higher and shoot the same sequence. Then try them lower and shoot the same sequence. Then try a sequence with a black reflector on one side of the model or the other and watch the effect it has on the shadows.
The above experiments should give you much food for thought and you'll start to understand what the lights are doing.
Re: Softbox Suggestions Please
In this shot of Malloy, can you tell where the black reflector was?