Is Medicating Your Sick Child In A Divorce Without The Other Parent's Consent Illegal If It's In The Best Interest Of The Child?

Location: Colorado (south/closer to Denver/Boulder)

**********Trigger warning for SH/suicidal ideation.**********

Hello. I (22F) was just in the hospital last night with my sister who made another self-harm attempt while staying at my father's house. My mother and father are divorced and have been for almost 12 years.

My little sister is 15 years old and has been diagnosed with depression and anxiety. In about March of this year, a therapist and doctor prescribed her Zoloft.

My father had custody over her last night and is extremely verbally and emotionally abusive. He was calling her smooth brained and thick in the skull. He does not give her privacy when in the bathroom or in her room. He abuses cocaine, weed, and alcohol, but he's pretty decent at hiding it (at least to law enforcement because it's so obvious to me, but they've never done anything about it).

My sister has had a few cutting incidents in the past 2-3 years. This was the first one in over a year, and the worst one. She had multiple/dozens of cuts on her wrist from a pair of really old rusty scissors. My dad drove her to our local hospital, was very combative with the doctors/security, calling her stupid in the car on the way, and then he just dropped her off and left her.

She called my mother, and then my mother called me, and we went to sit with her. She was in the ER at this time (in total for about 6-7 hours).

At some point my dad showed back up and just let himself in the room and started yelling and telling my mom that he is going to sue her with all this money, and to get ready to feel the wrath. He said that she purposely put my sister on Zoloft knowing it makes children kill themselves, and that she is a horrible mother. He said a lot of things, but I don't that is relevant to what I am asking. He mostly just made my sister extremely upset and was saying things to try and upset us all. I lived with him until I was 16 and fought to get out, so I know he likes to control and get you upset.

The doctors eventually had him escorted out as they were thinking in the best interest of my sister, and she wanted him out as it was causing her severe stress. She spoke with a social worker, and we have a safety plan in place to make sure she doesn't have to go back into his custody for the time being. This incident has also been reported to CPS, and the doctors said my father was really unpleasant and he was telling everyone my sister was on weed (tox screen was completely negative).

Basically, my question is: is there actually a way that my dad can get my mom in legal trouble for having my sister take medication? She did it without my father's consent, because she knew he would not approve of it (he does not believe in meds or vaccines), and the doctor highly recommended she try something. As far as I have heard, the medication is working, and this event actually stemmed from my dad finding the medication while going through her bag and taking it from her.

We are on the poverty line and cannot afford a court battle and I am worried this is going to be an issue, or that it would be grounds for them to take my sister and make her live at my father's and I am worried she will do worse if that is the case.