Thank you for your query.
You did the right thing. Ensure that your daughter's mouth is rinsed and make her take some cold
milk to dilute any ingested content.
The battery contents are no doubt corrosive but the very small amount that you claim has been ingested will not cause any harm. It needs to be diluted with food at the earliest. In case your daughter vomits or is exhibiting any other symptoms then she needs to be taken to the hospital.
I hope I have answered your query to your satisfaction.
Wishing your daughter an early recovery.
Rajiv K Khandelwal