Depends on if she wants to reef or if she just wants fish only. She'll need at least 10X water turn over per hour, a heater or a couple of heaters will be better if she's not reefing, a hydrometer, test kits for ammonia, nitrate, nitrite, ph, kh, "maybe more if she wants to reef." She also needs to decide what look she wants her tank to have natural etc. I would also get the materials needed to q.t. her new pets as she sets up the tank. Keep it simple a bare bottom 20 gal, a sponge filter ,"keep the sponge stashed in your main or sump until needed" a flower pot or pvc pipe .
hth
Max