Have you had any luck with your cat problem? Can I ask what breed she is?
I have the same problem with my persian cat - persians are prone to doing this.
I was given a bottle of the feliway spray, which is similar to the plug in, but you can put it where ever you like, which I found handy. You need to spray the area once a day, for a month or so (although the problem seemed to have stoppped from day one, I think its to make sure its well and truely stopped). You can use it pretty much anywhere. We used to have issues with the cat peeing on the bed, and although they are kept out of the bedroom, when we got our spare bed, about 2 weeks ago, I have just sprayed it a couple of times with the feliway spray and there has been no wee on there so far! The problem was such an issue before, that we had to replace our douvet and mattress! We have also been spraying everyday in a couple of areas downstairs that she wees on. We haven't caught her since.
I would also recommend that you have several litter trays for them. You are meant to have one per cat, plus an extra one. They should be different sorts/sizes. Eg, if you have a covered litter tray, you should also have an uncovered tray. The bigger the better too and they should be scattered around the house, so you know she isn't being "caught short"
I know exactly what you mean when you say that she looks at you while doing it, ours has done it while me a DH have both been there, and she had no worry about us seeing her!!
When we got our cat flap installed, this definatly helped too, alothough she doesn't go out much in this whether, it means she is happier as she can come and go as she pleases. She has also been seen going to the loo outside, which is great as hopefully by the summer, she will go to the toilet more.
I will also use the fliway spray when baby arrives too (I am due tomorrow) as I am worried about her getting jelous and the problem getting worse. I prob wouldn't put it inside the pram etc, as wouldn't really want baby breathing it in, but will give the outside a spray, so the general scent is there. It calms the cats and makes them feel comfortable, and should take away the need for them to urinate on the item. Have kept the door closed to the baby's room, and kept all baby stuff in there for now, untill it is needed. Except stuff like the bath etc which can be cleaned. You could use the spray to spray on your sofa too, to stop her going there.
Let me know how you are getting on and I seriously recommend all the above, it's really worked for us. As I said, I am due tomorrow so I understand the worry of it all.