Those leaves are looking healthy for your first grow, good work! She's looking a bit long in the branches (lots of space between nodes) which generally indicates she wants some more light. Are you using a weak light?
To answer the actual question, it sounds like you're growing a photoperiod plant, which means it's entirely up to you when you want to flip. I had one that I kept in veg for more than a couple of months because the first couple months I had some serious problems which stunted her pretty bad. Once I got all the kinks worked out and she got nice and big I flipped her and she finished strong. Things you should keep in mind when deciding when to flip: 1. Does she look healthy now? If not, you might want to correct the problems first as she's going to be more susceptible to problems during flower. 2. Do you have a enough room for her to keep growing after you flip to flower? They tend to take off and grow quickly during the first couple weeks of flower, so you don't want to run out of space in your grow room. 3. Is she big enough for your liking? Again, she's gonna grow more, but you may want a bigger plant so it might not hurt to keep her in veg longer. It's totally up to you at this point, experiment see what you like, learn and do something different the next time.
Happy growing!