how is it possible for jasper to control bellas emotions but she is immune to everyones powers??

Stephenie answers this on her website, link

[Copied and pasted from her website]

"How come Alice and Jasper can affect Bella with their supernatural powers, but Edward and Aro and Jane can't?

This question comes up at every single signing! The answer is explained in Eclipse, but I'm going to tell you all anyway, just so there's less confusion.

Bella has a very private mind. She can't be touched there. What Edward and Aro do is clearly a mental thing; Jane, also, works inside the head (Jane doesn't actually inflict pain on anyone's body, she just puts the illusion of pain inside her victim's head. It's a very effective form of torture). Conversely, what Jasper does is no illusion. He affects the physical body, slowing the pulse and upping the endorphin levels to calm someone, for example, or raising the pulse and pumping out the adrenalin to excite them. Alice, also, works outside the mind in the realm of possible realities. She doesn't see the thought process behind the decisions, just the outcomes."

well Jasper controls and manipulates emotions that are basically governed by heart. Alice never alters the future... simply has the ability to search through the different possibilities. Bella's MIND is a fortress not heart. Plus her future is independent of her MIND since being a mortal she cannot predict the future in her mind. Thus making her pliable for their gifts and not the other talents

Put simply Jasper's power only affects the physical body. It isn't a mental thing like Edward's and Aro's and Jane's are.

wow. i just noticed that. what a good question!! to bad i don't have an answer for it! :D sry

honestly doesn't any one read the books? she only sheilds mentall powers and jasper is emotional

Jasper effects the physical body not the mind.