That's not what people mean. You're not to blame for her actions.
They mean you're leaving yourself and your own career open to harm by not reporting it. That part is on you.
The responsibility you feel towards whether she loses her job or home is misplaced. These things aren't your responsibility and won't happen as a result of your actions. If these things happen it'll be purely as a result of her own actions.
You'd not be reporting her maliciously. If she wasn't doing bad things there'd be nothing to report! Therefore nothing that happens to her is your fault.
Her behaviour is escalating. First to the touching and asking to be tickled and now to snatching at you. She is the one carrying out her behaviour. If someone's life has to be negatively impacted by it, it should be her life, not yours.
If HR are carrying out disciplinary procedures and she's not listening to them, taking it on board and changing her behaviour, then firing her is the correct thing to do and the correct outcome for safeguarding the staff and pupils in the workplace. It's not something you'd cause or need to feel guilty for.
The reason I've mentioned for you to make it clear to others, including your boss, that you're being harassed is because reports can come from anyone. At the moment it would be so easy for a third party to make an official complaint that it looks like these two (you and her) are in a relationship and behaving inappropriately at work making an atmosphere and causing everyone else to feel uncomfortable.
I personally know of someone who was reported for sexual harassment at work, for flirty touching/banter with a friend. The friend was (according to the perpetrator) fine with it but the witness wasn't and the perpetrator got given an official verbal warning (I don't know for sure about the friend but may have been unofficially warned about their behaviour at work).
You don't want to get caught up in a situation like that, it's better if the report comes from you and you're officially noted as the victim of harassment and not seen as someone who may be a semi-willing participant. Don't risk throwing your own job under the bus trying to protect hers.
I agree with those who say to stop seeing her outside work. One, it puts any defensive claims from her that you're romantically involved into the territory of less likely to be believed. Two, it puts your status as the victim of her inappropriate behaviour as into the territory of more likely to be believed.
It's not only her you need to be crystal clear with - its the bosses, with your actions as well as with words. It's harder to claim any kind of harassment when you're voluntarily also hanging out with the person as a friend.
Abuse within romantic relationships and the mental impact of it, the altered thought patterns etc, that stops people walking away is more readily recognised now, but abuse within platonic friendships still isn't really seen in the same way by most people (but it can and does occur in just the same way).
You're feeling confused by her.
You're unhappy.
You're experiencing unwanted touching.
You're being followed.
You're feeling misplaced responsibility for the eventual outcomes of her behaviour.
You're being isolated from sources of support.
Her behaviour is affecting your professional reputation and your relationships with colleagues.
Your boundaries are being trampled repeatedly by her.
Her behaviour is escalating over time.
This is not a healthy friendship.