Which visa for adopted daughter?

Hi.

My wife is Chinese, with pre-settled status via the EU Settlement Scheme via Surinder Singh route. She has a daughter that she legally adopted before we were married who is living in China and who is under 18. We send her money for support every month and meet the UK's minimum income requirements. I am a British citizen.

What kind of visa can we apply for? I asked a lawyer who suggested that my wife switch to a UK spouse visa and then apply for her child to join her, but that has disadvantages (mainly cost, visa+health surcharge alone is over £3.5k). Can she apply on the basis of being my adopted daughter?

Thanks in advance for any suggestions.