18 yo using furosemide and hydroxyzine for eating guit and heart issues - risks?

hey i need some med advice for my gfriend (18f).gonna give u all the details tho.

background:
age: 18
height: abt 155 cm
known isuse: tachycardia
smkoer
no known mental stuff, but she won't get help

meds she's on:
furosemide and atarax
why:
to deal with guilt aftr eatting
furosemide to avoid water retention
atarax for no appetite & emotional relief

dosage (self-reported):
1-2 tabs each/day, sometimes up to 4

use periods:
feb 2025 - jun 2025
feb 2026 - now
she says when she sttops, feels urges all the time

behav patterns:
feels bad after eating even small stuff (like a nut)
if doesn't take pills, purges
used to restrict calories and overexercise (30-40k steps/day + running), work too much to hide it

mental stuff:
needs control & perffectionism
uses behavior as punishment for "failure"
pride from weight loss and self-discipline
misses feeling of that period but knows it's bad

current mindset:
wants to stop but also misses it, says urges won't go away
thinks things might get better when she has more control over her life

my worries:
combo of meds + purging + restriction
her tachycardia + possbile electrolyte imbalance
risks: hypokalemia, arrhythmias, long-term organ damage
behav getting worse with each cycle

qusetions:
how dangerous is this combo? esp heart risk?
what r signs for urgent help needed?
any short term harm reduction tips?
how to convince her to trust therapists again & support her better?

thanks in advance!