Then I think it will be fine.
I had a brownout recently while I was at my computer, but it stayed on and the monitor even stayed on without dimming. The only difference I noticed was that my fans slowed down. But I panicked and shut it down, which I was even able to do properly!
So once the power came back to 100%, I asked Phaedrus2129 about it and I learned that the brownout was harmless because I have a switching PSU. In addition, my monitor has a switching PSU too. He said that even when the brownout caused the power to be reduced to like 30-50% or whatever it was, I could have been gaming and I wouldn't have been interrupted. Well, I lost my internet connection because neither my router or cable modem have switching power supplies, but still.
So even major power fluctuations are harmless to good PSUs. I think it has something to do with having Active Power Factor Correction (PFC) or something like that.
So, I'm trying to say that even if she turns the hairdryer on while you're gaming, your system may not even notice.
Having active PFC, though, means that there's a boost converter present on the primary, which can keep the voltage up for the primary switchers. So that adds a little brownout tolerance vs. non-PFC and passive PFC SMPS.
But monitors rarely have APFC, and so don't have even the small margin the boost circuit gives you.