That’s an accurate translation.
We have two things going on here that you’ll see more of.
First is the ん.
Her line is an informal contraction version of 「何をしているの」. The following is taking place:
- The を particle is dropped. (This happens sometimes.)
- The い gets dropped. (In [verb]ている, this happens all the time.)
- The る before an “n” sound becomes ん. (This happens with some speakers.)
Further reading on this “r”-sound character becoming ん:
The second part is the の. This one is a very common grammatical structure in Japanese that we don’t have in English.
The way I like to explain it is thus: We constantly observe results, but not what caused the result. For example:
| Result | Cause |
|---|---|
| Your mother tells you to clean the living room. | Unknown. Why am I being asked to clean? |
| Your friend calls and says he’ll be late meeting you for lunch. | Unknown. Why will be he late? |
| You see someone kicking a vending machine. | Unknown. Why is he accosting that vending machine? |
When you seek to find out the cause, in Japanese you end the sentence with の:
- “The reason I have to clean… Is it because company is coming overの?”
- “The reason you will be late… Is it because your car broke downの?”
- “The reason you are kicking that vending machine… Is it because that vending machine ate your moneyの?”
But it doesn’t work only for asking for an explanation. It can work if someone is giving you an explanation:
- Mom: “After all, it’s your stuff that’s lying around the living roomの.”
- Friend: “Halfway there I realized I forgot mｙ wallet, and have to drive back homeの.”
- Vending machine kicker, upon seeing you watching them: “Don’t mind me. I’m just a weirdo who likes kicking vending machinesの.”
(I recently did a longer write-up on this use of の if you’re interested in reading more.)