Hi Poppy04 and welcome to bpdfamily
Setting boundaries can definitely be challenging, yet this is a crucial element of dealing with a BPD child. Your daughter was recently diagnosed with BPD, what led up to her getting this diagnosis?
What do you consider her most difficult or disturbing behaviors? You mention her not helping out around the house and feeling like she uses people. In what ways do you feel she uses people?
We have some material here about boundaries and limits that you might find helpful:
Communicate boundaries & limitsSetting Boundaries and Setting LimitsTake care and again welcome to our online community
The Board Parrot