Why didn't Anne Sampas become like Eve?
How come she didn't end up like Patrick?
They never explained it. I have a theory that maybe the alien DNA didn't take correctly in her, hence the weird offspring followed by death. Or maybe Patrick was the best match, so he got the "best" DNA and she was infected by whatever was left over.
In reality, it just seemed like the writers had no idea what to do with the character, so they killed her off in a burst of tentacle birth to focus on Patrick.