HSA Contribution Limit for Adult Working Child in the Family HDHP Plan

What is the HSA contribution limit for adult working child filing individual return, but included in the family HDHP plan of the parents?

 

I believe the child can independently contribute $7000 to his/her own HSA account since the parents are not allowed to use their HSA funds for a child who is not a dependent.  I would like to confirm this. 

 

My child is covered under my family HDHP plan. I have contributed the maximum $7000 to my HSA for 2019. My child recently started working and filing the individual return for 2019. She signed up for her individual HDHP plan through her employer (I believe one is allowed to have multiple HDHP plans). Since she is included in my family HDHP plan, what would be the limit for her HSA contribution for 2019? Can she contribute $7000 to her HSA independently because she is covered by the family plan?