How can I make it bigger or is it too late for tha...

She looks like she’s in the middle of reveg. If that’s the case, you should start seeing lots of new growth soon, leaves and branches. Revegged plants typically grow bushy as hell. Enjoy the ride!👍

Let it grow, give her a good drainage to keep the risk of moldy roots low. Get her some nice nutrients and learn from that grow. For outdoor plants I recommend a defoliation in the 3rd week of flower. Every fanleave get the best we have, the sunlight and the massive outdoor growboost comes from that leaves. Give her the chance to recover😊

That last part was a generalization and not a comment on your plant. I wouldn't assume anything with the amount of info given as far as yield or end size.

While I agree with "don't defoliate in future" sentiment, the context matters as far as whether a proper canopy can develop before the buds start forming. Less likely with an autoflower. Doesn't mean you won't get a large percentage of the potential yield, but the less it grows back, the more impactful it is. There's no making it bigger.. there's simply providing a good environment and feeding it to match that environment. It is better described as staying out of the plant's way, lol. Geentics are king. They are the potential. there's no magic products or magic technique that changes a leopard's spots. there may be small influences, but nothing turns a small yielding plant into donkey dick colas.

Too late.............you cut so many energy producing leaves off that you stunted it. Next time, don't defoliate.