Texas (and other if not all other states, I assume) have laws (called 'usury laws') that limit the amount of interest a lender can charge a debtor. The laws exist to protect consumers against unscrupulous lenders. However, "in the past decade, payday and car-title loan companies [in Texas] have used a loophole in state law that allows them to operate without interest rate limits. As a result, a payday loan for $300 may end up costing about $701 — the highest rate in the country, according to an analysis by Pew Charitable Trusts." See:
Masako Melissa Hirsch, ‘Opponents keeping up pressure on payday lenders in Texas,’ Dallas Morning News, September 27, 2014
As of September 2014, 19 cities (including Dallas) have passed ordinances regulating payday and car-title lenders. As a result, many such businesses have closed. For example, "in 2012, Dallas had 241 payday and car title loan stores; as of [September 2014], there were 177."
Id. However, the State of Texas has taken few actions to rein in the practices of such lenders due to the industry's lobbying efforts.
Can the lender sue the girl? Yes, of course. As I've written here many times before, a person can be sued anytime and anywhere for any reason. A lender can certainly sue a debtor on a defaulted debt (and collect attorney's fees, as well). The lending agreement is a contract, and the parties' rights are largely determined by what's in the contract. However, the lender's rights may be limited by city, state, and/or federal law. The girl should confer with an attorney regarding her rights. Many lawyers won't charge for an initial consultation, or will only charge a nominal fee.
I've read that payday lenders tell debtors they'll be arrested if they don't pay their loans. That's false. With some exceptions, it's not a crime in Texas to fail to pay a debt. Moreover, if the lender threatens the debtor with arrest, that would probably be a violation of the Texas Debt Collection Act, which bars (among other things) a debt collector from "threatening that the debtor will be arrested for nonpayment of a consumer debt without proper court proceedings" and "threatening to file a charge, complaint, or criminal action against a debtor when the debtor has not violated a criminal law." See:
Texas Debt Collection Act, Texas Finance Code, Chapter 392, section 392.301. Threats or Coercion, subsections (a)(5) and (6).
Each instance a lender claims the defaulted debtor will be arrested is a Class C misdemeanor.
Id., section 392.402. The debtor may also sue the lender and collect damages.
Id., section 392.403.
However, it doesn't violate the Texas Debt Collection Act to "threaten[] to institute civil lawsuits or other judicial proceedings to collect a consumer debt."
Id., subsection (b)(2).