Hi there
I think, I wouldn't stretch her to do 3h before the first nap. Most often baby need the shortest A time prior to the first nap. So personally with a wake time of 630a I'd put her in the crib at 9am. I think a 1h am AM nap is perfect really. Then I'd slowly add to the second A time - 5-10m every few days so she doesn't get Overtired. Stop at 30m added, and see how the total 2.5h does for her. This will push the nap to 1pm, hopefully she will still do a 2h nap and that will bring you to 3pm. Perhaps do lunch at 1230pm and the do your BFing when she wakes at 3ish.
Lastly, with a wake time of 630a, I'd really move your bedtime up to 630/645pm and see how that plays out. This will leave 3.5h before bed which she may be able to handle better.
Just my opinion! Hope it helps some!
Zoe