What are the boundaries of love for the sake of Allah that please Allah, and how can one differentiate between it and admiration, especially when dealing with a girl who has started to become religiously committed but I have doubts about her behavior and past? And are my feelings towards her love for the sake of Allah or personal attachment?

Continue advising the girl and helping her to repent and become righteous, with gentleness and affection, while striving against your lower self so that your intention is purely for the sake of Allah. Do not turn away from her unless your contact with her harms your religion or your worldly life. Otherwise, your companionship with her to invite her to goodness is beneficial for you if your intention is pure, for the most beneficial people to you are those for whom you are able to do good.