Study Abroad or Stay Home?

I got accepted into a program to study for 4 months in Australia. But the college I got accepted to doesn’t offer the classes I need for grad school. And neither does my home campus! I only need 4 credits left to graduate and my options are either studying abroad and then coming home to take those classes or just take them now over the summer to start grad school
early.

though I want to study abroad because I’ll never have another opportunity to do so, others tell me it’s a waste of money because I’ll have to go back to school again for the required classes anyways. Any advice is greatly appreciated. Thanks.

Is study abroad covered by your sxholarship? Is it affordable?
Sure, it costs money, but it’s money well spent if you maximize your opportunities there. Find an internship (I believe those are level for young Americans in Australia). Learn about your major subject in another context. Visit. Make cultural comparisons.
See if the university offers complementary classes you’d need in grad school (like French or Russian if you want to study math, bioethics if you want to go into medicine…)
Are you sure the classes you need for grad schools aren’t offered? Australian universities are usually very big and comprehensive. Email the departments and ask if they have similar classes.
You’re in college only once. If you can afford to go to Australia, don’t hurry to go to grad school, learn as much as you can, broadly, at the time when you can.

I would definitely support the answer above.

On a more general level, this is an opportunity that will enrich you a lot and broaden your horizons.
Even if you delay going to grad school a bit, this will not have been in vain but the opposite - you will be a better candidate even.