This is actually by her choice, in her book she discussed how she likes to be support actress and that allows her time and finances to deal with her other hobbies.. basically she an actress part time if you will :)
I Don't Know What You Know Me From: My Life as a Co-Star https://www.amazon.com/dp/0345806735/ref=cm_sw_r_cp_api_i_P-t4Cb1TJEVGY
If buying from amazon, please use smile and link to the EFF :) for internet freedoms..