iPhone 11 says I have 31Gb of pictures while there's none in it

Hello,

My wife have an iPhone 11 and google pictures.

Google pictures has all of her photos backed up on it, so she used the optimize button on it to clear space from her phone. Her current iPhone photos gallery is on about 37 pictures, yet when she checks storage setting, it shows that pictures take 31 GB worth of space.

How is that possible?

I tried to change the date on the phone to locate more "recently deleted photos" but there are none, that folder is empty.

Any ideas what can she do? we even bought more space on iCloud and yet photos are on 31 GB while her gallery is empty beside those 37 pics.

Thanks

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