I'd say it is her 3month growth spurt...she is doing great if she was going 6-8 hours & I think you will probably be at that point for a couple of months yet... 8-10 is reasonable at around 6mo, but then wakeups occur for other reasons than feeding, so you may get 10 hours between feeds, but other wakeups for developmental reasons.
Try to up her calories in the day & keep the extra night feed as small as possible... if you bf offer feeds more frequently & if bottle, bigger feeds during the day. As I think it is a growth spurt that has gone a bit off track & she has subsituted some day calories for night.