You need to talk to a local family law attorney in your county. It appears that you have grounds to ask a judge to give you legal custody of this child. I have no idea what "temporary guardianship" means because "guardianship" can only be granted by a judge & that is a probate matter - normally minor children cases are controlled by the Texas Family Code and it's referred to as "custody". If she merely signed a piece of paper, that is not legally binding and she can change her mind at any time.
Please talk to an attorney immediately.
The answer may be that she goes. You should file a Suit to get you rights as a non-parent conservator of the child. To become a legal parent. You can request an order to establish the status quo until the case comes to trial on a temporary hearing so that the child remains with you while it winds through the court process.
You do need an attorney. The parent may based on the limited facts presented in your question have a parental presumption. Only after an in-dept consultation can someone advise you on how best to proceed.
Bobby Barina's answer to a legal question on Avvo does not establish an attorney-client relationship. Mr. Barina offers everyone a free consultation to discuss their case. Feel free to call his office at 254-699-3755 to make an appointment or visit his website at www.bobbybarina.com for more information about his services.
You have not been granted temporary guardianship. People don't grant temporary guardianship. Judges do. If the person with legal custody shows up and demands the child, I see nothing in your facts that would protect you if you refused to return her. You need to hire an experienced family law attorney to advise you on the chances for obtaining legal authority over this child.
DISCLAIMER: This is not specific legal advice and does not establish an attorney/client relationship.
Sign up to receive a 3-part series of useful information and advice about child custody law.