That's a bit redundant in your case, Yuuka...

Possible translation issue; I'm not entirely sure about the proper usage of the verb 'butsukeru' which is most obviously 'to hit' but apparently can also be used as 'to throw' in some situations. But pretty sure it's more that she doesn't want to hit Bulbasaur with the ball.

Awww, poor conflicted Yuuka!

The pokeball only have to make contact, as shown in the anime. There was a few times where you just have to touch said pokemon and they will get captured if they want.
Although weird that it still shakes even when the pokemon willingly join. That and seems those that touch the pokeballs themselves usually come out whenever they want.

Or it could be like the game where you just throw and it opens in the air and capture.

Well, remember Yuuka, all you've got to do is not do this.