No, she was not a Buchanan supporter:
RNC communications director Danny Diaz shot back at Wexler: “Rep. Robert Wexler’s outrageous attack today on Gov. Sarah Palin is the worst kind of politics. Instead of engaging in a discussion on the issues, Wexler’s smears and accusations are detestable. If Barack Obama has any intention of engaging in a serious and honorable debate, he will immediately condemn these scare tactics.”
The National Jewish Democratic Council issued a measured statement, saying her hard-line stance on abortion is to the right of most American Jews and questioning her support from the Christian Coalition. The Republican Jewish Coalition (also doing its job) defended her in a statement that makes no reference to Israel.
http://www.politico.com/blogs/bensmith/0808/Palin_on_Israel.html
According to this video, Buchanan himself stated both she and her husbands were fundraisers for him.
http://www.youtube.com/watch?v=U9rZkJfKoEU&e