I'm going to look at each of the powers that are referenced by Harrowed and try to compare them between editions.
Power Name 4th edition 5th edition
Critter Spook -5 BP (negative), -2 w/ animals -5 Karma (negative), -2 w/ animals
Nasty Vibe 5 BP (positive), +3 Intimidation 5 Karma (positive), +2 Intimidation
Spirit Bane [Man] -10 BP (negative), pisses off spirits -7 Karma (negative), limited to mages, -2 difficulty to summon, +2 resistance (for the spirit) to banish
So the total BP value was -10 in 4th edition. In 5th edition, the total Karma value is -7. The quality's total BP value was -15 though, which means that it had an extra surcharge of 50%. I would surmise this is because the character doesn't need to be a changeling to get Nasty Vibe with this quality. So for a 5th edition conversion, I'd still use the 50% surcharge, making the quality a 10-Karma negative quality. However, because this quality can be taken by non-mages, who otherwise cannot take Spirit Bane, I'd probably bump it up to a 15-point negative quality.
TL;DR - I'd say 15 points for 5th edition.