It's definitely the right idea. Most people start by offering solids just once a day for the first week or 2 to see how it goes. I would just start with your morning session and then add one mid-day later. Generally you just want to offer solids an hour (or so) after milk since milk is the most important thing nutritionally and you want to make sure she doesn't decrease her intake.
Does she usually take a full BF at 9 before her nap? If she does, you don't want to interrupt that. I would just offer solids during A time, maybe around 8. Startingsolids earlier in the day gives time for any tummy discomfort to pass before bedtime so it won't disrupt nighttime sleep.
To that end, when you do start the late afternoon feed I'd give milk at 4 and then wait a bit for solids, maybe until around 5 or so. But if I were going to add a 2nd feed it would be around 1.
Does that make sense?