You need to tell us the company and type of test. Paternity tests (and the similar "sibling tests") are not used for genealogy and aren't anything we do here. What the test results mean depends entirely on the company that tested you.
Given how cheap they are now, I think you're much better off with one of the genetic genealogy tests. It also makes it very easy to compare yourself with other people who have tested, both people you might have used the sibling test for or random strangers that turn out to be related to you.
The primary companies are: 23andMe, AncestryDNA, FTDNA, and MyHeritage. They each have sales often.
If you were not related to this woman, your results would show zero. Because you did not supply the name of the company (and I wouldn't be familiar with it anyway, as it is not genealogy), I don't know if 14% probability means she is more likely to be your niece or your cousin, or if that's what they expect half siblings to show. Read their FAQs and ask them if you're still unsure.
If you test with a genetic genealogy test, please return to ask about that if you have any questions.