It does need a bit more work, yes something perhaps as you said something around the shoulders or head. However, I agree it's a huge step up. The secondary color gold alone makes a significant difference.
On the slavery question if one wants to go deep what Lorna was describing from her retcon it was serfdom not slavery. The difference being slavery at its core is about the legal ownership of persons and serfdom is about a Lord forcing people to work in a community under threat of violence against their community from his Knights.Frankly speaking, most clothes we have in the West could be considered as from slave labor. Payment for workers in countries that make most clothes is minuscule.
But that's not the argument I'm "going with." Their purpose is scouting and intel. Lorna buying the dress advances that goal, same as the girls being there at all and putting up Mysterium. If Lorna's done something wrong by buying the dress, then the entire team is at fault for buying in, most especially whoever came up with the plan. But back to scouting and intel, playing along goes further toward gathering information than not. You can look to Hercules Mulligan for a historical example of how it pays off. As a tailor, he learned vital strategic information for the revolution by working on the clothes of British officers rather than refusing service.
And I would say this all fits for Lorna. She's a veteran, she knows sometimes you have to at least temporarily go along with bad things to reach good outcomes. Especially with this being a To Be Continued, we'd have to see what the next issue does.
Though the term serfdom from an American context doesn't have much resonance which I am sure why that word wasn't used. Also, someone had to get their hands dirty doing retcon why not have it be the more morally ambiguous member of the team. If Duggan was writing her like a Golden Girl heroine like certain others tried doing about 95% of the fan enthusiasm would have evaporated. Also, its information that will almost certainly matter in terms of next issue and the downfall of Gameworld.