Hi cornelia96,
Good core question about applications. You're obviously asking it specifically from your perspective but I'll give you a general answer. We can get more specific about your specific case in a FREE 1 hour assessment / brainstorm session.
An MBA program is ultimately an academic study program. Your only prior experience in a similar environment is your undergrad degree. Your GPA says a lot about:
1) How seriously you treat studies
2) Your ability to cope with academic pressures and excel
3) How you compare to other applicants (somewhat objectively measured)
4) What your academic areas of strength were in the past
Those are all good indicators of your potential success in a rigorous MBA program. So you GPA is an important element of your application.
That being said, it was a performance measurement when you were far younger, had less work experience and were still figuring things out. So if it's not great, that's not a fatal problem. You just need something else more recent (objective) to counterbalance it. Your GMAT score can do that as well any challenging certifications like a CFA etc that you've subsequently completed.
How important your GPA is to your individual case depends on the balance of your experience and how well you can hit the mark the leadership potential and values markers that each AdCom is focused on.