Not sure if it was you I mentioned this too or not, but have you looked for any other signs of colic?
Often babies will feed (read soothe) through their tummy pains - the rhythmic action of suck swallow actually makes the pain and cramps go away.
Of course, this only adds to the problem. So if she is feeding CONSTANTLY for 7 hours and crying when pulled off the breast, I would seriously look at this.

Do you burp her? How often? Are you eating anything that could be upsetting her - this could be anything like milk to garlic to chilli to (think this was Kitt3n) peanut butter. Sometimes your diet can cause bubs to get very windy, this will be causing her pain, and the feeding is a comfort and soother.

Feel her tummy, low down - is it firm, hard? Or nice and soft? Does she have any pain you can pick up on when you touch different parts of her belly?
Give her legs a circle around. Lay her down on her back, hold her legs together on her shins, just under her knees, and move her knees together in a clockwise circle, so you move them around, and up to her chest, ad back around. Make sure you take them quite wide and do it for a few minutes.

A warm bath can help soothe, as can baby massage. You can use chamomile oil in a carrier oil to soothe. Again, rub her tummy in circles, clockwise, with an even pressure.
This will all help anything move through.

If you are concerned about your supply itself, then grab hold of the lactation cookie recipe, it works wonders, and is tasty .

Have a look inside her mouth, is there any white residue looking stuff in there, on her tongue? She could have oral thrush, which means you could have it on your nipples.

Is she having issues with silent reflux? Not all reflux babies vomit everywhere constantly, many throw up in their mouths, without much fuss, but the constant acid reflux will make their throats sore, the feeding again soothing, but worsening the problem as well.

There are just so many things, it can be overwhelming. But run through them and check them off, offering formula won't actually solve the problem in the long run, could make it worse, and give you a whole new set of issues (tummy problems, constipation...).

Anyway, I am no expert, hopefully Barb, MantaRay or Marcellus can offer some sage advice, these are just some of the things that I came across through our years of BF, and thought there may be some things there you hadn't known of or tried yet.