It took about a week plus a few days for the owl to completely recover from its flight from Britain to the American east coast, and all the way to the Umbra Witches' apartment in New York City. During which time the aforementioned Umbra Witches spent gathering up Halos that they traded in with Rodin in exchange for the currency of the Wizarding World, more specifically the most valuable coins of the British enclaves, Galleons, mostly because of the fact that it was relatively easy for Rodin to simply melt down the Halos into Galleon-shaped molds and applying the necessary magic that reinforced the structure of the coins. The fact that the Halos were already made up of gold certainly helped. Thanks to either an off-handed comment, or perhaps an intentional hint, from Rodin, Heather learned that the location where she would spend a good portion of the year was a hotspot of activity for both lesser Infernals and low-tier to low middle-tier Angels, similar to the sacred mountain of Fimbulventr, but at a significantly lesser extent.
Which was something that prompted the bartender/weapon smith and young Umbra Witch to strike a deal. In exchange for new weapons, Heather would provide Rodin with Infernal Orbs and Halos (as payment) along with summoning the Infernals (which would most likely be members of the Succubus tribe thanks to her Contract with Lilith) to infuse a piece of their essence into the weapons. While Rodin was free to build whatever he wanted, Heather did request that the first weapon out their deal was going to be something that could appeal to the two most prominent aquatic members of the Succubus tribe, Scylla, Horror of the Sea, and her sister, Charybdis, Maw of the Maelstrom, whom Heather had been interested in forming secondary Contracts with in order to not only have more options when it came to summoning but also acquire at least one aquatic form for Demon Masquerade, and she wasn't particularly picky regarding which one of the two she got, though hopefully she would acquire a secondary Contract with both of them, especially when the two members of the Succubus tribe were noted to make a surprisingly effective tag-team in combat despite the differences in their physicalities within their respective entries in The Infernal Compendium.
Once the week was over and Heather sent her response to Hogwarts with the owl, she and Viola left the city of New York for the city of London only days after the owl left. Exiting a crimson portal from The Gates of Hell in an alley that no one would pay attention to and entering the streets with the primary shopping center of magical Britain, Diagon Alley, as their destination, which they eventually found after about two hours (not only because they were searching for the pub known as The Leaky Cauldron (which served as the entrance) but also because they took a break to get some lunch). And fortunately for both the Umbra Witches and Diagon Alley itself, the two arrived at the same time as another soon-to-be first year at Hogwarts, a bushy haired girl, her parents, and someone who was apparently a teacher which allowed Heather and Viola to enter the magical shopping center without causing a commotion, as Heather would have been very unlikely to hesitate literally smashing through the entrance to Diagon Alley with a punch or kick with My Red Requiem enhanced by a shotgun-esque blast of magical energy once the young Umbra Witch ran out of patience. Unlike the family that arrived at the same time as Heather and Viola, the two Umbra Witches didn't need to enter the bank to exchange their money for the currency of the Wizarding World due to already carrying more than enough money to buy Heather's school supplies on hand thanks to Rodin.
The actual shopping went quite smoothly for the Umbra Witches… for the most part as there were a couple of instances where things almost turned chaotic. The first one occurred when Heather stumbled upon the book series about 'her' supposed adventures at the bookstore, which was obviously fiction and finding the writing to be the worst case of bad writing ever written, of all time. The second one occurred when Heather was waiting for her turn in the clothing shop to get her robes, the school uniform of Hogwarts (much to her annoyance), but there were two boys already in the store getting fitted. From what she could overhear of their 'conversation' (which was actually closer to an argument), both of them wanted to marry Heather in order to get their hands on her inheritance money. Something that didn't appeal to the girl in question at all as (from what she heard) she would have merely been a trophy wife for whichever one got her, which prompted her to launch the pair of Halos she had been twirling on her fingers, in order to relieve herself of boredom, in the two boys general direction. Both Halos ended up hitting a few pins in such a way that the pins wound up digging into the boys in a quite painful but ultimately harmless way.