I am sorry to hear your friend is in this difficult situation.
Here is a webpage with advice to pregnant women from women who have had abortions and now suffer emotional problems because of it: PASS Support Site - "Best Advice" page
Some are pro-choice, some pro-life. There is a whole range of opinions and ideas there.
I really think she should tell her parents, if only because abortion is an invasive procedure which CAN result in complications that need to be treated. She needs to be able to go to her parents for help, rather than possibly delaying treatment to conceal the abortion, if there are physical or emotional problems that need to be treated. I think that, because she was raised in a religion that tends to be very pro-life (even if she doesn’t consider herself Catholic anymore), plus planning to abort without any support from her family and probably feeling like “it’s the only choice”, she is at risk for having a hard time coping with aborting.
Nobody should feel forced to abort for lack of other options, if this is a truly “pro-choice” (rather than pro-abortion) society. She found out she’s pregnant only a few days ago, so it isn’t much of a surprise that she isn’t ready to have a baby right now. Fortunately, pregnancy does last nine months. That is enough time to find help and resources.
Here are some places that can offer help with issues like telling her parents, finding a place to stay, school or work, arranging an adoption, etc. :
http://www.nurturingnetwork.org/
http://www.birthright.org/
http://www.pregnancycenters.org
http://www.catholiccharitiesusa.org/programs/
Below are some maternity homes that will offer shelter and other services to pregnant women, some which focus on adoption and some that don’t care whether or not the woman wants to choose adoption. Perhaps knowing that she doesn’t have to stay with her parents will make it easier to avoid feeling coerced to marry the guy.
http://www.gladney.org/html/pregnant/livewithus.html (this one has several locations in TX)
http://www.harborhouse.org/
http://members.door.net/smithlawn/ (another TX one)
http://www.maryelizabeth.net/
There are others out there–those are just some I found links to right away.
Please encourage her to think carefully about how having an abortion will affect her emotionally. I think, for teen girls in particular, it is tempting to want to think abortion will just “erase the problem” and put everything “back to normal”, but I have encountered so many women who experienced lasting effects from an abortion, I don’t think that is realistic. Pregnancy leaves a lifelong impression, whether it ends in a birth, a miscarriage, or an abortion.