I don't really see your point here. How can Constance Marten's parents force a 37 year old woman to do anything? If she wanted psychological help then she could get it but what can you do if someone refuses or doesn't think they need help?
She has been estranged from her parents since 2012 - according to Constance Marten because they disapproved of her having children with Mark Gordon. It is clear that nobody knew about the baby before they fled.
You do understand that her parents don't control the family trust and the money she gets? It is administered by trustees, a London firm of lawyers, and it is not clear who set it up from press reports. Could be one of those family trusts from generations ago (her great grandfather was a Baron) or could have been set up by her brother who sold the ancestral home and some land for £34 million in 2013.
Clearly Constance knew enough to write to the trustees for additional money beyond her monthly allowance. She got money for a car, and camera equipment - I presume the trust would have paid for private medical treatment but she didn't ask - from her court appearance I don't think Constance thinks she needs help.