Afraid to be alone....

So some follow-up from the bed time battle....(from August 13th).
After deciding that we would take her to Chuck E Cheese or one of those inflatable indoor gyms if she's able to stay in her room all night - or basically to keep from waking her parents up every night. She's been doing great not waking us up at night, but now has either been waking up her younger brother to convince him to go sleep in her room with her (who knows what time of the night that happens) or the other morning I found her asleep in her brother's bed! Well I guess I've been getting some uninterrupted sleep and I shouldn't complain. I haven't heard any complaints from her brother yet.
I think the main reason she's been doing this is that she is afraid to be alone. If she needs to go upstairs or downstairs for something (regardless of the time of day), she always cries for someone to come with her. Again, other than the crying being annoying, she mainly convinces her younger brother to go - sometimes after lots of crying and shouting.....now that's not so good.
Not sure if this is normal (whatever "normal" means) for someone her age - she will be 6 in just a few weeks? Anyone else have kids that are afraid to be alone?