Can Adopted Child get visitor visa while applying for citizenship (MN1)

Hello;
My British husband adopted my 16 year old biological daughter after step-fathering for 10 years.
He also obtained Turkish citizenship a while ago, adoption happened in Turkey (while he was resident in UK). Unfortunately her passport application was rejected as adoption was an Overseas Adoption but not a Hauge Convention adoption. Turkey is a convention country. So they adviced us to apply for British Citizenship through registration first (MN1 form).

I have a family permit and my husband is already in UK.
Can our daughter visit us in UK on a Standart Visitor visa while waiting for the decision from Home Office?
Would they reject her visitor visa as both parents are in UK and she will stay with us based on intention not to leave after 6 months?
What is the safest and quickest visa to apply?