Can I just point out she is not taking on Tesco. She has no relationship with Tesco. She does, however, have a contract with Bruntwood, and it appears they have broken their own contract by the arrangements they've made with Tesco.

I'd also like to point out that she already has a lot of competition within a short walking distance of her store so it's not like she's complaining about competing with the likes of Tesco and Sainsburys as she's doing this already, but to have a competitor right next door, when your tenancy agreement gives explicit reassurances that that scenario won't happen, is unfair.