I think #2 is the best composition and will probably be the one with the least obstacles such as the background in #1. I definitely do not like #3 because it looks like her head is sinking into the back cushion.
A final note regarding the size of the head... I followed a workshop with Margaret Carter Baumgartner this summer and one of the most important things I learned was to stop making those monkey-sized (her words) heads. She insisted that a portrait be life-size and I admit that applying this rule has really helped me get a more realistic painting.
Great pictures! Can't wait to see the painting.
