A wider crotch is pretty par for diapers, it improves their capacity and performance when flooded, but yes it does add a lot of bulk between the legs. That's just part of the "diaper experience", and it's a feature that a lot of DL's enjoy. Being IC, you will get better performance from a wider crotch if you can tolerate it. I've also found diapers with a narrow crotch are much more likely to leak when sitting down, whether you wet while sitting down or shortly before sitting down.
Many places will give you the advice to "pre-fold' a channel in the front for better drainage from the front of the diaper to the back, to improve all-around performance, but that won't work as well with a narrow crotch.
If you're going to have to rely on diapers daily, you'll eventually figure out what you have to do within your circumstances to avoid leaks and other problems, but it'd be good to figure that out sooner than later of course!
Different brands of diapers can vary a lot on how they fit in the crotch. Most are wide, while a few are narrow. The thickness of the padding varies greatly. You might find better success sticking with a wide crotch but that has thinner padding, so you end up with a smaller overall amount of padding between your legs. You didn't say what diaper you're currently trying the size medium and large in? At least being a girl you have less luggage to worry about down there