Wake windows / bedtime

We’ve had this issue once or twice where my 22 month old has napped later than normal - I get stuck on what time to do bedtime.

She usually sleeps 12-1:30 and goes to bed at 7:15/7:30 so around a 6 hour wake period.

She wouldn’t nap at my MILs earlier so she fell asleep at 1:30 in the car and I transferred her to the cot and woke her at 3pm.

When this has happened in the past we’ve tried to settle on a mid ground of 8pm but found she would wake super early the following morning like 4:30am. So I’m not sure whether to go closer to normal bedtime (more 7:30ish even though I know she will spend 1hr + babbling in the cot) or much later because she had a late nap?