To extend this more into speculation that does fit the pattern (and evidence?) though:
AKA abandons MB somewhere in Europe (or another “dream” location). MB is unaware because he has provided a reason for a temporary separation (meeting, business…take your pick!) = PATTERN
MB continues her trip solo, pottering around…unaware. Sends postcards, makes phone call to SL. = EVIDENCE. Something happens to MB in Europe (or other dream location not Oz).
BUT conflicting EVIDENCE shows MB’s passport returning and cash being withdrawn from her account and visiting optometrist in Grafton. All seemingly provides “proof of life” of MB back in Australia. A Smoke and mirrors trick in other words And made possible if the POI is a known document falsifier, fraud and immigration dodger and has the capacity to cover his travel tracks (at the time!). Plus, he is aware (and no one else apart from MB is) of MB’s name change and thus provides another diversionary advantage for him. Should MB be reporting missing at the time and LE go looking for her in the UK, she has been travelling as FNMR. If they look for her in Oz, they can see proof of life as MB. Smoke and Mirrors!