Who is Andrea Bishop?

Andrea Bishop is probably an Easter Egg, made just for those viral videos. Though some say she is an android. Here is a good link that explains a lot about all the Androids featured in the Alien series (Andrea was added as well): AVP-Wikkia-Synthetic

About the Bishop we see at the end of Alien3, he is a totally different model, the real Bishop is broken (dead) and tossed in a garbage pile.  At one point in the movie Ripley goes to reactivate him so he can read the ships log to her. There is a lot of debate over the blood in that last scene and what Bishop's motives where as well, because of the different cuts to the movie that were filmed.

Regardless it isn't the same Bishop as in Aliens, it's 2 different Models. Most people will tell you the second Bishop did not care for Ripley's wellbeing at all, that he only worked to secure the Alien Queen for Weyland Yutani.

Here is a video of the scene where Ripley revives the original Bishop (can't embed, its not in YouTube):Alien 3 - Talking To Bishop

As you can see, the Bishop we know is completely destoyed, sadly. 

I believe she is an android manufactured by the Weyland Corporation. She is either less or more advanced than David 8. 

The Bishop at the end of Alien 3 was an actual human iirc.

In ALIENS: COLONIAL MARINES, Michael Bishop turned out to be an android.

Michael Bishop is human.

The character in A:CM is called Michael Weyland. I don't know why.

@S.M

I thought so too, but how would you explain his appearance in AVP? 

Different guy. One is called Charles Bishop Weyland; the other is Michael Bishop. Same actor - different roles.

Be interesting if Predator was fully rolled into the continuity - is Hudson a robot based on Jerry Lambert?

Or is he Lambert's great, great grandfather? :)

@S.M

Ah I see, perhaps a twin that skipped a generation.

It was strange in PREDATOR 2 that Bill Hudson was named Lambert. You should make a discussion out of it, it'd really be interesting!