Sounds like you are back-filling or testing a defense in a public forum. Not an accusation, an observation.

Your girlfriend won't be the person who builds a case against you, that will be a district attorney. If she has evidence, like child pornography, saved on her computer to incriminate you she actually may also be commiting a crime; it depends on the narrative that a criminal investigation follows during the course of its research.

You're correct that the accusation and investigation can negatively affect you, however any investigation is good if you are innocent and are looking to protect your reputation.

The more to take measures to destroy, and tamper with evidence, the more guilty you may look. Googling things like: 'how to erase my hard drive permanently' or 'how to avoid punishment for this crime', etc. also look suspicious.

If you're innocent you should welcome an investigation and cooperate fully. A D.A. isn't going to just pick up and run with a case without trying to understand the witness(es) motives.