May I know how old your little girl is? You are absolutely right. In most cases, the adult teeth will cause the milk teeth to be mobile and subsequently lost, making space for the adult teeth.
In this photo, it looks like the two side adult teeth are erupted but the two front milk teeth are still present. My advice will be to seek an opinion from an orthodontist to check for the reason why this has happened BEFORE extacting the milk teeth. Sometimes it may be because two lower adult teeth are missing and in this case, you might want to keep the baby teeth for as long as possible.
The orthodontist will carry out a thorough examination and take x-rays if necessary before advising you whether the milk teeth needs to be extracted.
I hope this helps and good luck!
