I bought a duplex and one tenant said she won’t pay new price

[Norma Rosa]

So I purchased a new duplex which is very exciting and now I’m a landlord. I took over a letter introducing myself to my renters and one of the tenants is perfectly fine but the other one says she can’t afford that much and is not going to pay. She has a large 2/1 and pays $500.00 a month when the average for a one bedroom is $700 +. Because she has been there for 5 years I have to give her 3 months to move but does that mean at her price or mine? What can I do as I already have new tenants waiting and are going to pay $1000.00.