There is a way that you can take a conservatorship over an adult as a family member. Depending on state laws, I believe all you need is 2 psychiatrists to say that this person is unable to care for themselves and is completely dependent upon you for financial support. The next time she goes to the hospital for an episode, you can have them keep her there until she gets checked into an inpatient program (short or long term). At that point, you get to make most decisions for her until her doctors see remission of her illness such that she could support herself or could function in a group home of some type.

It's not your responsibility to pay to keep her in an apartment. If you care about her (and I know you do), the best thing is to get her into a program and have her treated and watched over a period of time to see if she's not just fooling the one psychiatrist about taking her meds. Even if she is, it may not be the right kind or amount for her illness. She may not tell him/her everything that's going on like delusions, hearing voices, alcohol abuse, etc.

In some states, New York for example, the law would be on your side:
http://mentalhealth.about.com/cs/sch.../commit204.htm
(not saying she's schizophrenic, but bipolar is a serious illness as well)

Oh, and look at this related article. Three paragraphs up from the bottom it describes a program starting up in Florida...Jacksonville that is coming to the rest of the state:
http://mentalhealth.about.com/cs/leg...commitmaio.htm
It continues on to the second page.

Here are by state NAMI centers for support of those who know someone mentally ill:
http://www.nami.org/template.cfm?sec...our_local_nami

Here are some coping tips:
http://www.nami.org/Template.cfm?Sec...ontentID=26499

Hope this helps some. You do have some options. It just takes some time to get educated about the state laws and how much it would cost you to get her into a more structured environment. But I think there are state funded programs that would be free as well.