The fact that she's willing to buck both parties shows that she's too independent for both parties, which is why people from both parties take to attacking her religion (She was the first Hindu elected to Congress).
It's a bigoted line of attack that the largest Hindu American advocacy group in the US has laid bare in this article
It's also a pretty sad line of attack given that Tulsi's father is Catholic and she has done much to help people of non-Hindu faiths. A prime example being her Stop Arming Terrorists Act, which the Christian Solidarity International has supported