This could be some flirting, some passive aggression. Both birds are at an age where hormones will start to play a part in their behavior. I would move the cages away from each other and not allow this intrusion. Parrots are territorial. Some more than others, and most territorial behavior is over nesting sites. But in captivity, the cage is all the parrot has that is “theirs”. Goffin’s can be tricky. It’s a species I specialize in and I’ve had my own Goffin’s for over 35 years. What seems like ignoring can really be careful observation and waiting for the chance to strike. A Goffin’s can seem to be very casual and not interested in another bird one minute, and then launch an attack the next. Male Goffin’s especially can be vicious towards female Cockatoos. Both of your species are known for mischief. This could go either way. The birds could end up bonding, which would leave you out. Or they could get jealous of each other and start fighting. Allowing the Galah to enter the Goffin’s cage and eat his food is playing with fire. It seems innocent, the Goffin’s seems to be ignoring the Galah and allowing this, but he is more likely observing and waiting for his chance to go in and defend his territory. I feel like it’s time to set boundaries and have each bird’s cage off limits to the other. This will help prevent other behavioral issues as the Cockatoos continue to mature.
Thank you for asking Lafeber,