It was more of an emotional reaction to the fear of seeing her father on a London street than just logical thoughts or any preconceived plan. What came next was like a smooth dance between them where Arthur was quickly roped into playing the role of her boyfriend again without prior consultation but complete with convincing public displays of affection.
The magic key was a kiss between them that would protect Rachel from the critical eyes of anyone she knew or feared. She initiated a quick series of simple steps and turns after exiting the shop to stop them and engage them both in performing the role of a young, loving couple. Within a matter of seconds she pulled Arthur in for a kiss.