Anathema handles a lot of their early network building, at least among her and Ellie's friends.

She writes Serpens - then Serpens' mom. She promises to tutor Serpens' little sister, Lyra. She discusses safety with Fay, who puts their house under a Fidelius with Sirius as the Secret Keeper, and how to arrange tutoring and meetings over the summer is then a complicated question. Anathema and Lyra end up just meeting in public at the Leaky Cauldron - it's safe enough right now, and Narcissa Malfoy seems interested in making statements to passerby anyways.

She writes their roommates, and then the other Ravenclaws, and the other muggleborns she's even vaguely acquainted with. She warns them about Voldemort, about the attacks on muggleborns and their families last time. They set up a small network already - someone digs up the newspaper reports on attacks from the last war, finds they had a range of times they happened in (always at nights) and the more nervous students arrange phone call check ins during that time - they'll then call Professor Reynolds if anything's wrong. (Nowhere near everyone's part of that network yet, and probably if nothing actually happens it'll fade a bit in people's minds, but - it's getting them talking. It gets them everyone's phone numbers, and the addresses of anyone who's moved since Fay delivered their Hogwarts letter.)

(And to few of those she trusts, Anathema sends instructions on how to cast the Killing Curse and on how to clear your wand of it so Priori Incantatum won't catch it. It's better than your family dying, and she also gets help finding the relevant laws then sends copies of the parts of the legal code about defenses in court for casting it.)

She digs through her mother's vaults - according to the goblins, Bellatrix hasn't accessed them at all since the end of third year - first for paired mirrors and lucks out on a set probably meant for propping up on vanities. They're big, with pretty frames and enough reception to talk from other sides of a continent. She bundles up one and sends it to Elodie early in the summer.

(Sirius gets a hold of a new wand and starts joining their family spars every day. He contacts Dumbledore, explains his case, and offers his dead mother's home as a headquarters for Dumbledore's own network - the Order of the Phoenix. Sirius still stays with their family, though, and he isn't even the Secret Keeper for Dumbledore's safe house. He stays up late at night with Fay planning, discussing which members of Dumbledore's network might be more likely to side with them.)

Anathema arranges a meeting with Dumbledore, to explain Bellatrix. He examines her gravely, and promises he'll do what he can.

And then - training, mostly. They pass all their OWLs with flying colors (slightly lower flying colors in Potions and Herbology, but, well, they at least could still take the NEWT in them if they wanted). Their Transfiguration, History, and Defense OWLs have notable mentions for high scores. They need to pick classes for next year - Anathema does NEWT Transfiguration, Defense, and Charms, and arranges to test into Music (joining the fourth years) and Astronomy (joining the third years), and signs up for Ancient Greek (joining the second years).

Anathema's somewhere between 'exhausted' and 'manic' much of the summer, and she takes to curling up with Ellie as she writes letters.