The answer to this question is going to depend on your jurisdiction, which is California. But in general, you are referring to two different documents: a power of attorney and a medical proxy. The POA gives someone the power to handle another person's finances and sign documents on their behalf. The medical proxy lets another person make healthcare decisions for them if they can't for themselves.
If you are worried about having access to your friend's money, your friend would need to draft a power of attorney making you her attorney-in-fact. However, there can be a lot of issues involved. I recommend that your friend contact an estate planning attorney in her area.
I recommend having your friend execute either a Durable Power of Attorney Over Assets or a General Power of Attorney. Also recommend that you contact an experienced estate planning attorney to draft the document. Best regards.
No legal representation exists by virtue of this answer. It is recommended that you contact an attorney directly for a more complete response.