Will daughter have to pay high French taxes?

Your daughter would benefit from the usual French rules (and the substantial inheritance tax allowance for children) concerning your estate, should you pass away; but neither would apply to any inheritance she may receive from your husband because the French rules do not protect stepchildren.

Under the new rules, both of you could leave your estate to whoever you wish (if you are English), for example, entirely to your daughter from your previous relationship.
However the rules do not change the fact she will face high taxation if inheriting from your husband.