Sindel sounds like a real sweetie! Doesn't talk? Do YOU talk to her? I'm sure you already know this but the more you talk to a bird, the more likely they are to pick it up. I constantly speak to Shasta. There's not much silence in my house, between Shasta and I having intellectual conversations (What's funnier? the bird or Dr.O being intellectual lol...) And the other birds having their "I AM THE LOUDEST TODAY" contest lol. The result is that from me talking to Shasta constantly, telling her what I'm doing, how my day was, or my newest theory about Steven Hawking (lol) She learns the same behavior. Shasta is VERY vocal. And she picks it up QUICK! That's why there's no swearing in my house, lol. Apparently the last time she was boarded over the weekend she had some pretty "Choice" words for one of the employees’ lol. So I would try that, just constantly talk to her; when you’re making dinner tell her what your making, what's in it, how your cooking it, who's recipe it is.... You can read to her also. If she's like any Umbrella I've met she probably loves to cuddle, so cuddle and read to her
A great thing to read is Parrot care/behavior books. Parrots love to hear their names, and it gets their attention, so when you’re reading to her replace the words "bird/parrot" with Sindel. And use Excitement! in your voice. It's never too late for her to start talking.
I would really think about changing her diet, like you mentioned, from seed to pellet. But do it slow if you choose to change her. You said she doesn't pluck or scream much. You don't want to make sudden changes that effect change that. How much cheese does she get? (Birds are lactose intolerant....)
Are there any pics of Sindel around RTB? I'd love to see her
