Have you tried a later nap as well? I know jack needs one really long A in the morning to build up enough tiredness over the day. You might find that a later, capped nap means she gets more tired by bedtime?
Also, fwiw, Jack has averaged an hour's day sleep since he turned one and is sleeping so much better for it. I don't need to cap cos he doesn't nap for long anyway, but if G was on one nap at 7.5 months it is conceivable (to me, anyway) that she just needs less day sleep. J does a 13.5 hr day on average, with a 45 minute - 1hr 20 minute nap after about 7 - 7.5hrs A and then about 5- 5.5hrs to bed. He's done that since around the time he turned one