Sometimes improvement can be very quick, a matter of a few days. Sometimes it can take longer, it just depends on what is going on. The B's are very safe, extra will be excreted, so there are no worries of overdosing. I would stick with it for a couple of weeks at least, unless you see improvement before that. I always go a few days beyond symptoms stopping. If a bird isn't eating well, for any reason, they can become deficient. Whether it's illness, not eating due to molt, being kept from feeders by higher pecking order birds, deficiencies can happen. It could also be an illness/disease causing the symptoms, but the B vitamins will not hurt anything. You can either pop it whole into her beak and she should swallow it, or you can grind it up and mix into a bit of moistened feed, or whatever she will eat, and give it to her that way.