Hi! My DD is the same age and I found that she will do 4hrs A after a long first nap, but then a late pm nap was giving us EW, even when I cut it short.
Believe it or not, this is the very start of the 2-1 already! (Although it's a slow process). So your options are either to cap the am nap to get an earlier, longer pm nap but still have longer to BT, or cap the pm nap to get an earlier BT, depending on what your DD prefers & what suits you too.
What has worked for us is capping the am nap. This gives her a shorter second A time too. It's taken a bit if trial and error but the sweet spot for us seems to be
Wu
A: 3hrs-3.5hrs
Nap 1 : 30 mins
A: 3.5hrs
Nap 2: 1.5hrs
BT 3.5-4hrs after waking.
I tried the other way round with a 1.5hr am nap and a 45 or 30 min pm nap, but as I said above, it gave us EW...it works for other people though & might be worth a try first as it's closer to what you're already doing.
As with any adjustment, shorten the nap you want to cap gradually (15 mins every 2-3 days) to avoid OT & remember that A time after a capped nap usually needs to be shorter too.