Pee Problem

So, I'm having a bit of a problem with Mokey. I went away to Dallas for a week, and had a friend of mine look in on my cats. There were no problems...until I got back. I'm guessing that Mokey was mad that I was gone for a week (actually, it was less than a week...I only left them for 4 days), and she started peeing in the corner of my room. Well, I scrubbed and cleaned and then I sprayed that "Nature's Miracle" (the spray that's supposed to get rid of the scent, so cats won't go back to that same spot). Then I covered the spot with a towel. Well, she peed on the towel. Then, I put her food there b/c I was told that cats won't pee where they eat. Wrong! She peed right next to her food bowl. Then, I put tin foil there b/c cats are supposedly frightened by the sound tin foil makes when they step on it...not Mokey! She peed on the tin foil. Then, I put a new, fresh litter box there (since my vet said that maybe she didn't like going to the bathroom in the same litter box that Gobo uses)...she peed NEXT to the new litter box, but not IN it! So, I cleaned, scrubbed and vacuumed the entire area...then I put TV stand w/my keyboard right in the corner where she likes to pee. THEN, I put the new litter box right in front of the keyboard/TV stand. Things were good for 3 or 4 days...until last night....when she peed in the opposite corner of my room! ARGH! I'm taking her to the vet tomorrow morning to see if it's a urinary tract infection or something of that nature, but I have a feeling this is just a behavioral thing...and if so, I don't know what to do!!!!

I'm so stressed and frustrated by this all, and I'm not getting any sleep at night. I
could close my bedroom door at night, but then I can't snuggle with my kitties. Gobo is a great snuggler, and I can't lock Mokey out without locking Gobo out (since the litter box and food are not in my bedroom, so they need the door open to get to those things). So, if I keep Mokey out of my room at all times, then I have to also keep Gobo out at all times...and that stinks! I don't know if Mokey is still angry about my 4 day trip, but I'm just getting so upset by this all...and I honestly don't know what to do! I'm actually hoping that it's a UTI or something like that, so I can give her meds and she'll stop doing this. But, if it's behavioral, I'm just S.O.L.!