The other consideration is Ripley doesn't know what an Alien egg looks like in ALIEN. She has no correlation between Brett and Dallas fate and what they are becoming. As far as she is concerned, they're trapped and part of the hive mass.
Ripley doesn't actually see an egg until a lot later in 'ALIENS' when she goes searching for Newt. So no, she can't make a connection there.
-Windebieste.