Interstate Issues: Changing Custody Across State Lines

My question involves a child custody case from the State of: Oregon and Texas

Long story short: My niece was awarded custody to a family other than biological. She has lived with them for the last 14+ years in Oregon. She is 16 now. We pay for her to come visit us in Texas in the summer. She has told my wife and I about abuses going on in the home. We have reported these to DHS, but they feel it is not enough to displace the children (They have 4 other adopted children). My niece does not want to go back to Oregon, however the court appointed Custodial Parents have said no to letting her stay with us. I've purchased her a ticket home as I do not want to be charged with kidnapping.

Here are my questions:

I figure if she lets that plane takeoff without her on it she immediately becomes a runaway, what are my legal responsibilities (other than notifying her parents within 24hrs)?
Is the financial burden on her parents to purchase another plane ticket?

We want her to stay and live with us, and will be filing a petition to change custody; What is the likelihood of this going our way? Neither of her parents have jobs, and one just got into trouble with the Law for theft, and selling stolen goods.

Is there anything special to have the custody hearing moved to Texas, or would it have to be done in Oregon?

Since I do not reside in Oregon, am I correct that the harboring a runaway would fall under Texas Law, and is there any federal law I should be wary of?

Thanks in advace!

Interstate Issues: Changing Custody Across State Lines