It looks like you're definitely making progress with the first nap - 1.5 hrs is really pretty good. Is she waking happy from that one? I suspect the tiredness issues are a matter of her adjusting to the longer A times - you've gone from 1.5 hrs to 2 hrs - that's a really big jump. I would say to keep working on the A time extension - but just do 15 min every 3 - 5 days. So if her first A time is now 2 hrs, keep it there for at least 3 days. If she naps at least 1 hr, keep her next A time also at 2 hrs. If she naps less than 1 hr and you cannot extend her nap (either with pat/shh or pu/pd), then shorten that next A time.
As you're extending her A time, keep that extra A time really low key. I think it was around this age that my dd suddenly started needing a much longer wind down, so about 15 min before I'd usually start her wind down, we'd go in her room and have "quiet play" for a bit, then go into the wind down. So you may want to try that. At 7.5 mos, there's so much more going on in her world, that she just may be having trouble settling down to sleep, so lengthening that wind down while extending her A time can certainly help.
hth
michelle