My daughter rented with a group an apt at school in Wash DC.. the walk through is complete the apt. was left impeccably, and she gave the landlord some new tenants, she also vacated a week early, but paid for a full I am guarantor and I think the landlord does not have the deposit or need to wait the full 45 days to return it,
He said he did not want to do and threatned to take her to court, I am a landlord in NJ I do not think you can go to small claims court for this, please give me your opinion

I'd love to give my opinion, but I don't understand the question. While a landlord can decide to use the deposit towards unpaid rental, that's the landlord's decision not the tenants. If your daughter hasn't paid her last months rent, the landlord can take her to court for it.

Yes, while he may apply it toward the rent after he shows you did not pay on time, adds late fees and the such.
But he can take you to court if you did not pay the last month rent

I agree with the previous posters...

It's HIS decision to allow the deposit to go towards rent - not yours or your daughters.