If she has a valid passport, then all she'd need to do would be scare up the money.
Does anyone have evidence that she has a valid passport? I know she and KH went to Hawaii for their wedding/honeymoon but that's part of the US, so no passport needed. I haven't read any indications that they ever planned any trips to other countries, so I think it's possible she doesn't have a passport.
Only about 1 in 3 US citizens have passports, so that's not at all uncommon. Amazing but that's the way it is.
I assume that if she applies for a passport, the local police will be notified.
She could possibly drive into Canada but I assume that there's a covert GPS locator on any vehicle she might have access to.
Most of all, I think, would be lack of familiarity and a resulting lack of confidence. I can't recall ever reading that she's been out of the country.