Hi Angus,
This sounds familiar to what many here experience with their children. I'm so sorry your daughter is struggling Does she accept her BPD diagnosis?
I don't know of any easy way to detach (or, in your case, wean her off your financial support). Although, lately for me I had a

realizing that
I'm the one who experiences some kind of separation anxiety when I stop enabling my son.
On the Family Connections BPD website they talk about the importance of setting limits and not letting yourself become overwhelmed taking care of a BPD loved one. That can mean getting a therapist for yourself or, at the very least, setting up a support strategy when you start to wean yourself from the soothing you get when you support her.
Some people here do it in small increments so there is a long plan in place with milestones, or rewards for making changes in lieu of unquestioned support. For example, for every $500 she makes, you will contribute the same.
Part of being BPD is a desperate need to cling while simultaneously resenting any dependence. In that sense, it's easy to understand why she takes the money without being grateful for it as it confirms for her that she and others believe she is not capable, something she likely resents.
When she cut her wrists in the past, what happened?