No, try to get the treats and distration to her BEFORE she gets aggressive.
If you don't do it before, then it would reinforce. If it's soemthing she
LOVES then have it ready and right there so she never gets to aggression.
Play can act as a treat too if she is a player. The idea is whatever you use
to have both cats present and do it before agression starts. If she still
gets agressive, immediately cease treats and give her timeout in another
room. Doing this consistently ought to train her into a better attitude.
Also, it really sounds like she is not into petting yet. I would not pick
her up, but rather let her come over of her own volition. I bet you will see
a difference. It sounds like, she doesn't want to be on your lap (some cats
are just not lap cats. They may like affection, like to be near you, like to
be pet next to you, but do not like lap sitting. It's just how they are.
Sounds like maybe your new kitty is like this. You need to be patient and
just let her come to you on her own. Lots of play sessions with both cats
present will reinforce friendship between all parties.) so do not force her.
That alone might end the attacks.

And this is the crux of your problem. You are forcing her into something
she does not like, she gets agitated, and then takes it out on the other
cat because he's within range. If you continue to do this you in all
likellihood will cause things to deteriorate between the two cats and
could end up with an all out war on your hands.
Stop making this cat sit on your lap and deal with her on her terms.
Also concentrate on doing pleasurable (for her) and positive things in
the presence of the other cat so she associates good things with him.
You are just going to have to accept the fact that this girl is not a
lap cat.

Megan