Perhaps she feels "too" alone when you go upstairs to bed. As you said, she doesn't do it when you are in another room... that's probably because she can still hear you.

I take it you haven't had her long?

Personally, I would just ignore it. If you go to her, you are only going to reward her for being noisy. She will learn that yapping and howling gets her your attention, which isn't going to help and is only going to make the problem worse.

Yes, do get up and go to her if you feel she is being noisy because she needs the toilet... but don't get up if it's just for attention (I know it can be really hard to tell the difference).

Or, you could put her bed/crate in your bedroom. Alot of people don't agree with this (I don't in a way, unless you are willing to let them sleep in your bedroom for the rest of their days). Then gradually move her bed/crate out of the bedroom and further away, until it's back to wear it was originally.

My puppy used to sleep in my bedroom (I was prepared to have her in there even when she was older). She had a crate just opposite the bottom of my bed. When I put her in there and I then got into bed, turned out the light... she would start whining, yapping and barking. It got very frustrating, I will be honest with you. I was worried it was because she needed the loo, I didn't want to ignore it incase she then messed her bed! So I felt so frustrated and stuck... I thought "what if I go to her thinking she needs the loo, and infact she just wants attention... I will be rewarding bad behaviour"... it was difficult.

I made sure she had a last pee outside right before bed. That way, when I got into bed I knew that when she started yapping it wasn't because she needed the toilet. I ignored it COMPLETELY. I didn't budge when she yapped/barking/whined. In the end, I would put my MP3 player on LOUD so I couldn't even hear her yapping (everyone else in the house could though lol). After a few nights she stopped She would just get into bed and once I turned off the light she'd get comfy and go to sleep.