Snakes take a lot more time, effort, stress, understanding and energy than most ppl think. My 2 have drained me more than my almost 6 month old golden retriever pup. I understand your family started this by purchasing one as a gift, however, you are the caregiver. It's completely up to you to learn care, maintenance and proper treatment.
Mites are 100% treatable at home. Less stressful to the snake than a trip to an incompetent pet store as well. My suggestion is that you start doing a LOT of reading and slowly build a snake care box. Everything you need to maintain your new no legged friend from PAM to extra bedding, a soaking/ temp tub for cleaning or bad shed due to poor humidity. I keep spare bulbs of various wattages for the inevitable time one burns out or the temps change and I need one stronger. But then, I tend to lean on the side of overkill and preparedness.
Good luck to you and to little Zari.