If you have health insurance, she is young enough to be on your plan and this is covered. If she has no health insurance, there ends up being no charge. The kind of rehab one gets while destitute isn't pretty, but it's there. My brother was in and out of rehab for 15 years and didn't have a penny to pay for it. Addiction is considered a disability and under disability, people can get covered by state insurance. Don't let money get in the way. Take her to the ER and let them refer her to the local detox.
I'll add that things may be very different in Texas. I'm in Massachusetts, which is like the alternate universe to Texas but there are destitute addicts everywhere and they manage to get help somewhere. Start with your local ER (maybe just call them first) and see what they say.