my daughter passed away recently and before she did the hospital gave power of attorney to her girlfriend or so we thought.

First, please accept our sympathy for your loss.

In terms of your question, there are two different issues. The first is liability or fault and the obligation to pay compensation. In a case like this, that would typically depend on whether the hospital was negligent, or unreasonably careless, in choosing to honor the POA. If the POA looked legitimate and valid on its surface, then if there was some defect that would require a closer look or some more detailed verification, the hospital would most likely not be liable, since persons and institutions may rely on valid-seeming POAs. On the other hand, if they did not do even the basic level of verification, such as reviewing the actual POA itself--i.e. they simply relied on the girlfriend stating orally/verbally that she had a POA--they would be liable.

Second, though, for compensation, there has to be damages, or some non-emotional loss (emotional harm is generally only recognized when inflicted deliberately, such as by a stalker or serial harasser/bully or when it is a by-product of being near a loved one when she suffers a lethal and traumatic physical assault or accident).

In this case, there may not be compensible damages or injuries, if the hospital doing this understandably upset you and hurt you emotionally, but did not do anything to, say, shorten your daughter's life. It would be worthwhile, however, consulting in more detail with a medical malpractice or personal injury attorney, to see if perhaps there is some compensible damages, but at first blush, there would not seem to be.

You do have the option of filing a complaint with the state's medical licensing board about this, which would not result in compensation but may result in at least some small sense of justice.