How should i go about asking to transfer the lease on my name to the landlord?

I've been living in this apartment for 8 years, but the lease is under my ex girfriend's name who lived here only for the first 4 months of the lease, then she left. I kept renewing it because she didn't mind. But now she wants her name off the lease the next renewal comes up. I am on lease as an occupant and i have been paying the rent with my personal check which they never contested. I'm really worried that the landlord might not want to transfer the lease to me, as give the option to rent it under my name. I always pay my rent, never give problems. The price is a little under but they raised the rent by 25% on the last lease renewal. Thats when they chose not to apply the rent Stabilization anymore. What should i do? Should i have my ex to call the landlord's office and say that she is leaving but I am staying in the apartment and if they could give the preference for the apartment? What would be the best i could do and maybe have the opportunity for her to call them and deal?