raising the rent or holding it at its current rate

[Joe C.]

I have a great tenant for 2 years in that she pays timely and never asks for anything. She pays $1,900/month in rent. She is a doctor and her husband an engineer. I was thinking on raising her rent by $50/month. My expenses went up $40/month. On the other hand i am thinking about not raising her rent b/c she is an excellent tenant. Feedback would be appreciated.