This may vary depending on the country. But for the US, there are 3 criteria:
People are classified as unemployed if
they do not have a job;
have actively looked for work in the prior 4 weeks; and
are currently available for work.
Criteria #1 and #3 are fairly straightforward. Criterion #2 may be a little subjective and so we have the following clarification:
Actively looking for work may consist of any of the following activities:
An employer directly or having a job interview
A public or private employment agency
Friends or relatives
A school or university employment center
Submitting resumes or filling out applications
Placing or answering job advertisements
Checking union or professional registers
Some other means of active job search
So if your someone has actively looked for work in the prior 4 weeks (which includes the above activies), then she is counted as unemployed. Otherwise, she isn't.
Source: BLS, "Who is counted as unemployed?", which also gives some of the major questions (in the BLS survey) that determine employment status.