WE have a special needs trust in place for our disabled daughter for years. She is now 21 and we have power of attny. Can we make investments for her

You will not be liable for the investments that lost money - everyone's investments lost money these last few years !  You said the Power of Attorney was "done when she turned 18".  I'm not sure what you meant by that, but once your daughter turned 18, she is legally an adult, even if she cannot make decisions for herself.  now that she is 21 you should pursue a guardianship for her.so that you can continue to be her decision makers.   Its not that the trust or the Power of Attorney supersede each other as much as it is they address different things.  The Power of Attorney allows you to make decisions, and the Special Needs Trusts allows you to keep money for her needs, and still qualify for resource based benefits like Medicaid.  Is your daughter registered with DDD?  If she is, you can ask for a guardian through DDD however, it is my nunderstanding that it takes several years.  You can also privately hire an attorney to do the guardianship for you.  PLease call my office if you would like more specific information.