Hi, thanks for your enquiry. Your Daughter has absolutely nothing to worry about- as the property she intends purchasing will be her main residence, the standard rate of Stamp Duty will apply. The new additional rate Stamp Duty rules are only applicable to people who purchase further properties, which are not to be lived in (ie buy to let properties). Therefore, the fact that your Daughter already owns a buy to let does not change anything and she won't be liable for Stamp Duty at the additional rate.
I hope this confirms the position to you.
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