The Sixth Amendment is the section of the Bill of Rights that states that any US citizen has a the right to:
1. Have a speedy trail.
2. A fair jury.
3. An attorney (hired by the citizen or provided by court)
4. A chance to confront the witness.
5. Obtain witnesses in their favor.
The points mention above are more specific on the Sixth Amendment. What the woman in the scenario has the right to is to obtain witnesses in her favor, by doing so her friends are force by law to attend court by the use of summons. Leaving them with no choice but to testify.