Thanks for using Bitnami. We haven't tested this yet on our side and we do not have any guide related to this, but I notified our documentation team for checking it.
We highly recommend you to create a backup of your current WordPress data so you can restore it in case it goes wrong
I have found a guide in AWS official documentation on how to resize a database instance. You can check it and try to resize yours. Note we haven't tested it, so we can't give you support on this.
As mentioned, you can create a backup of your current data, and restore it in a new deployment in which you can set a higher db instance type from the beginning in case you find issues manually increasing the current database size.
Hope it helps,