Bella is careful.
Bella is careful to go to the magic shop during lunch - not at night, not when her parents might notice her leaving home, not when her teachers might notice her skipping classes. She is careful to wear her crucifix, carry her holy water gun, keep her demon whistle ready to hand. She is careful to wrap her occult purchases in disguising packaging: chip bags, gym clothes, grocery totes. She is careful to restrict herself to spells that are necessary - whether "necessary" means for the result or for managing her mercifully limited dependence on the damn things is always carefully recorded in opaque code in her notebook, and if the ratio gets too low, she goes cold turkey outside dire emergencies for at least three days. This is uncomfortable, and it kills her class performance and her temper for those days, but she has to be careful. Her parents don't want her doing magic. They're afraid she'll get addicted. (Done.) They're afraid she'll get snapped up by the USADI, drafted into casting more than she can handle or things that shouldn't be cast at all. (Not done; and another reason to be careful.) They're afraid she'll get a spell wrong and hurt herself. (Not done; yet another reason to be... careful.)
She is confident that witchery has saved her life at least twice, possibly as many as four times; she's sure it's saved others more than that. A month ago she located the hiding place of the Gem of Amara, determined it ludicrously easy to find, and conjured it to her for safekeeping in Forks under considerably more sophisticated wards placed gradually over the course of weeks. (Not in the house; any vampire with a non-vampire demon friend could bypass that protection and she doesn't want to put her parents in harm's way. But in a house, because the protection is non-negligible; USADI experimental reports say that squatters count as living human residents, and she can get into the basement section of a consistently occupied old Victorian close to the city walls without bothering - or alerting - those who make it their hangout.) With this gem more securely stowed, it will at least take longer for some vampire or other to come across it, render themselves invincible, and slaughter an entire metropolitan area before USADI calls in something sufficiently heavy-duty to get around the damn thing.
She's looking into how to destroy it, but while Forks has the advantage of safety, it also has the disadvantage of a relatively cruddy magic shop. The Witchnook is capable of special-ordering things, albeit with a lag time of weeks or months, but Bella's not sure how far to trust the proprietor. She supposes her parents don't know she's a witch yet, so it can't be "not at all", but, well. She'll come up with some other books to order in the same batch, as cover.
Bella is careful when she goes out at night. She wears her cross, she carries her holy water gun and her demon whistle. She sets her alarm clock at maximum volume for fifteen minutes after she expects to be back, with a note taped to it for her parents, in case she runs into trouble. And usually she doesn't go out at night at all.
Tonight she needs a spell ingredient that cannot be out of doors during the daylight without losing its potency, though, so if she wants to get it home at all, she is going to have to spend ten minutes walking to the Witchnook, pay for her twilight powder, and spend ten minutes walking back.
Forks has walls.
She'll be okay.
She'll be careful.