I think Babs has known from the outset that she didn’t have any claim to the land, she has hung on, either hoping that the OP didn’t cotton on to it, or enjoying the “woe is me” drama of it all.
I reckon if she has any sense she will put her hands up now she has had the solicitors letter, say fair cop gov and shift her stuff. She might try to come to an “agreement” with the OP about any thing that has been planted this year, which is fair enough since she has presumably looked after the plot well over the years, improved the soil, kept weeds at bay etc. if the previous owner had no interest in it it would now be a jungle of alkanet, dandelions, brambles, nettle and dock.
Or it will rage on until there are more dead bodies than an average episode of Midsommer.