Betta Fish: My in-laws got my daughter a betta fish while I was away

Hi guys me and my hubby went away to Bali for a couple days leaving my daughter with my in laws and in the time they got her a betta fish.

We only learnt about the fish through a video message sent to us and the tank they put the fish in was wayyyy to small and they kept the poor guy in there while we were away.

Ps my in laws don’t speak English and I don’t speak their language. We communicate through super broken English.

When me and my hubby came back we went to buy a new fish tank but my mother in law doesnt like big tanks and to avoid getting into trouble my husband suggested we get a smaller tank first

We got some substrate(sand) two water plans a hidey hole and some other stuff.

When we came back with all the stuff they kept insisting that bettas don’t need that much space
I know the tank I got is not big enough. But given that they are already making it an issue. getting a bigger one would be harder.

We are moving back to our place after the holiday season and hopefully we can bring the fish back with us.

Just wanted peoples opinion on whether it’s adequate for the time being.