Why qibble? Why not?

I'm on two HP fic yahoogroups, one called Riddlefics and one called Prof. McGonagall's Workshop. I posted my Tom/Minerva WIP on both and got a nice critique back from a person on PMW. This same person just posted on Riddlefics that she needs a beta for a T/M story that has a prologue, three chapters, and an epilogue. Which is how my story is structured. It doesn't sound like it's a complete plot rip off, although it has 1950's parts and post GOF parts, but it sounds close enough that I had a little flash of burning, seething fury. I think I will ignore it and try to focus on actually writing my story, but now I'm a bit concerned about posting anymore of the WIP. Luckily I didn't give a plot outline or anything to this person. It peeves me. Should it?