tobacco/drug cat

Sister Yaniko (Snuff Cat)

I
Alice
You most likely mean the sister of the heroine from the anime/internet meme "Tabakoshka".

What is her character like?
Since this isn't a canonical, major title with a written biography, the sister's image has evolved from memes and fan interpretations—and she's usually depicted like this:

Caring, but tired. She worries about her sister, but is already exhausted by her habits and lifestyle. In memes, it's often depicted like this: the sister comes to visit and immediately dons a respirator or a hazmat suit.
Pragmatic and straightforward. She doesn't beat around the bush and says what she thinks. She can be harsh with Tabakoshka, but she does so out of a desire to help.
Patient. Despite all her irritation, she doesn't abandon her sister. This emphasizes that behind the harsh words lies a strong family bond.
A bit cynical. Due to constant problems with her sister, she developed a peculiar sense of humor—often sarcastic.

Yaniko's close friend, Mimiko, is also a catgirl, but the complete opposite of Yaniko. She's called a drug addict or a medicat. She used to use drugs, but now says she doesn't.

Main character traits
Caring but strict, Mimiko genuinely cares for her friend and constantly tries to talk her senses: getting her out of sticky situations, dragging her home from a dark street, getting her to eat real food instead of fast food. And she does it all the time.

(I hope I got the right character, since I couldn't find her properly on Yandex)

This is a cat girl (neko-chan) with a severe nicotine addiction: she tries to quit smoking, then relapses again, and her struggle with the habit is presented in a comedic manner, but with very realistic and sometimes repulsive details.

Character traits
Contradictory and vulnerable, Yaniko realizes her habit is harming her and sincerely wants to quit, but she keeps slipping up. Her struggle with addiction isn't about willpower, but about a weakness she's not ashamed to show. This makes her seem very human, despite her feline features.
Ironic and self-deprecating. The heroine often finds herself in ridiculous situations because of her habit, but instead of dramatizing, she looks at everything with humor. For example, in desperation, she might cover herself with nicotine patches and then comically try to get rid of them.
Lonely, but not bitter. Yaniko has almost no loved ones, her life is rather marginal, but she doesn't become cynical or angry towards others. She's weary and humbled by her weaknesses, not aggressive.
Spontaneous. Yaniko's decisions are often dictated by spur of the moment: sometimes she firmly resolves to quit, sometimes, faced with difficulties, she gives in immediately. This impulsiveness makes her behavior unpredictable and adds a touch of comedy.

Plot
The story takes place in a world where humans and beastmen coexist. The protagonist is Yaniko Sato, a cat smoker who lives in unsanitary conditions, is constantly fired from her job, and is mired in debt. She recognizes her addiction and tries to break it, but the urge to smoke always proves stronger. Because of her addiction, she can't work full-time and has no family except her sister, who rarely visits her due to the constant smoke and garbage in her house.

In her attempts to kick the habit, Yaniko finds herself in ridiculous situations: for example, she might cover herself head to toe in nicotine patches, only to end up with a cigarette in her mouth. She even has nightmares about her lungs being completely burned out and her life being over.