My daughters roommate told her to move out . So she did now she wants next months rent and won't give her her half of security deposit back . What can she do about this

First... a few facts need to be available.
1. Is your daughter's "former" roommate renting the property?
2. If so, was your daughter included as a tenant on the rental agreement?
3. Who did your daughter pay her security deposit to? And does she have a receipt?

Your daughter may not have a legal obligation to pay further rent if:
1. She vacated the premises before additional rent was due (and there is no lease agreement)
2. No obligation for a notice of intent to vacate the premises (30-day notice) was required.

I'm NOT an attorney but I have been involved in landlord-tenant actions for a few years.

Yes you need to provide a lot more info.

Is there a written lease or rental agreement ?

Was your daughter renting from the landlord

Was your daughter renting from the roommate

If they both rented the apartment together from the landlord, then basically the room mate had no legal right to kick her out, since her legal relationshiop would have been with the landlord.

If she was a sub-renter, from the roommate, with no written lease, she could have been asked to move out with proper notoice

So it depends a lot on who she was renting from.