<human>: Could you distill the essence of the text into 1-3 sentences?

We've had Mittens for 3 years now (she was my roommates before I moved in here, and she adopted me as her fulltime owner). Last week my girlfriend and I adopted a new kitty, a white domestic short hair with beautiful eyes, and named her Abra. She's a very placid cat, while mittens is very territorial, she'd hiss and growl whenever Abra came near, but never attacked her. Her outbursts have decreased, but there's still some animosity in the air. Abra doesn't react in anyway to Mittens' threats, she was a stray before we adopted her, so we think she's use to intimidating cats. 

Normally Mittens is a food vacuum, she'd eat anything and everything (even one of my boogers and piece of onion once). Her favorite time of day is when she's fed. She'd yell until the food bowl was placed on the ground. These last few days, however, she's been very apathetic about food. She doesn't eat that much, and when she does it's not with the same vigor she once did. Could she be feeling depressed over Abra? How can we remedy this? It breaks my heat seeing her do downtrodden. She hasn't really been acting differently, but the food is a big deal for her.
<bot>: adopted a new cat. Current cat who loves food has become very apathetic towards it and doesn't eat as much as she did.