Does my daughter need to hire a lawyer and do the police always have to read you your right when arrested?

When your daughter failed to appear in court a bench warrant for her arrest was issued.  Typically, for a matter such as this, the police won't actively pursue someone.  Being taken into custody generally occurs only if another offense of some kind has been committed and the warrant turns up in a background check.  Either way, however, it must be dealt with.  Unfortunately, in this case your grandchildren were subjected to the site of their mother in handcuffs.  At this point she would be well advised to retain an attorney to help her sort all of this out.

As for her not being read her rights, basically, the Miranda warning (the reading of your rights) must only be given if a person is in custody and then questioned.  Any questioning before being taken into custody is legal.  However, if a person is in fact in custody and then questioned without being Mirandized then any statements made cannot be used.  The two exceptions to this: the statements were voluntarily and knowingly made any way (ie the defendant waived his rights); or the questioning was incidental to the booking process (ie. name, address, etc). So unless your daughter was questioned after being arrested she did not have to have her rights read to her.