Silly Lilly, my nutty cockatiel

Question
I have had Lilly now for almost 2 years and she is more like my child than a pet.  She is a Lutino Pearl and has some interesting quarks.  I got Cosmo, my male last October and he is slowly maturing but is still very much a baby and is so sweet.  The problem is that Lilly absolutely HATES all birds.  She only wants to be around my husband or I.  When Cosmo  tentatively and respectfully approaches (he is very well behaved towards her) she might hiss and try to punch him with her beak or she will get away ASAP.  They never fight but I just really want them to be friends and comfort each other when we are not alone.  Will Lilly ever accept Cosmo?  Random question, is celery ok for a treat?  They love it and wont eat any other vegetables.  One more thing, when ever I type on my laptop Lilly climbs up me and has to sit on the key board.  One thing, she does not lack attention!  Is she doing this just to be close to us or just to absorb some heat from the laptop.

Answer
The main question I cant help with but I do know after being with there people for so long in this case say two years the handfed parrots becomes so used to its people it may not accept new birds into the "flock" its very normal all that can be done is let time take its course and see what they think of each other in another week/month ect ect. Celery is fine as a treat msot birds love any type of lettuce also/apples/grapes/carrots are favoerites too. I'd say both she wants to be near you and be warm lol my lovebird would do that all teh time as well come and pick at the keys.