Renter changes mind and stay at low rent?

[Marci Stein]

My tenant of 2 years gave notice to vacate ,  so I offered her a lease at 900 a month , which is $200 less than her current rent. ( she’s alone now, and  I was afraid of a vacancy. ,) but She said no renewal . 
So i advertised the house and got many people interested for $1100 . 
but now because of Covid , she wants to stay  for 900  . 
she’s a great tenant , but I’ll lose 

$ 2400 a year  in rent with her lower rate 

Would it be unreasonable to ask her for more , maybe 1000, even though I sent her the new lease for 900? Nothing signed yet . 
Thanks