Landlady chasing rent arrears 2 years after dro

I owed my Landlady rent of one month due to losing a job, delays in benefit payment and then struggling to pay debts. She knew I was taking a dro and agreed that the arrears can be included. This was 2014 and the rent has been paid on time since 2013.

Out of the blue she sent a text last month demanding the arrears to be paid on 1st November and a rent increase of £100 per month. I didn’t agree to either. She has now sent a letter by email today, demanding immediate payment of the outstanding arrears by 1 nov and increased it by £100.

I understand she can start proceedings to evict which I’m fine with but can she now demand rent arrears to be repaid that were included in a dro?