BES probably has the best advice and she's got a huge advantage over most other posters...she's actually female so she's got a better idea than most of us, the unique challenges that women face when carrying a handgun
One thing you won't be able to avoid, and all of us have this - you wind up with a box full of holsters that don't work for you. It's a part of figuring out how to carry. Don't shy away from it...it's going to happen; you will have a shoebox with a couple hundred bucks worth of holsters that just don't work for you. May as well get started on it
And, the stuff that doesn't work, you can flog on the Equipment Exchange here. You won't get all your money back, but you'll get some of it at least.
If you want to stay appendix carry (and as a fat guy, I recommend it...if I can make it disappear with my gut, anyone who weighs less than I do should be able to make it disappear even easier), try a
Comp-Tac 2'Oclock holster. It doesn't work for everyone (I have one and for me it sits too high...but again I'm fat), but the people it does work for, love it. I don't know if they make a version that works with lights but it's a start.
My usual standby now is a
JM Custom Kydex Wing Claw AIWB. I have one for my Sig P320, G19 and Walther P99 and they all basically disappear the gun. I'm waiting on some neoprene wedges to make the Walther and G19 disappear even more, but the full-size P320 hides under a light t-shirt, completely.
Again I don't know if he offers or sells a holster that'll accept an on-board light...he also has a 7+- week lead time now, and they're not cheap. But, they do work. I'd recommend the "extra tuck" option at the minimum; it creates a bulge in the underside bottom of the holster that pushes against your pelvis, forcing the grip into your stomach some more; the wing claw rides against the back of your belt under your waist which pivots the gun even more into your belly; effectively hiding the grip completely without making it more difficult to quickly draw from concealment. It's great, in my opinion.