Jade, How much blood is coming out? Is it only coming out when she wees or is it coming out when she's lying down, like on bedding etc?
I'd say it's normal for there to be a small amount of blood (but usually dark, not red) coming out when a bitch wees even 7 weeks after whelping - but I wouldn't expect considerable amounts of red blood coming out on bedding that long.
Here is some info on SIPs:
https://www.saintfrancis.org/wp-content/uploads/Subinvolution-of-Placental-Sites-in-Dogs.pdf I know people might be fed up of me recommending Avidog, but I highly recommend you join the Avidog membership scheme and gain access to their Facebook group as a result (only available to current members) - where you can ask very very experienced breeders and Dr Gayle Watkins, for advice on issues like this. As you've experienced, vets just don't know much about repro health and I firmly believe breeders have to almost 'steer' vets with what they want if they are going to breed - and for me, Avidog offers that opinion and steerage! Membership is $49/month and you can just join for one month to get the advice and help you need, and then cancel. You also have access to all their courses for that month, including their flagship A-Z course (which you can print out to have forevermore!). They are lovely people and incredibly experienced across the group, almost every scenario you can imagine has been faced by those in the group. And A-Z itself is worth the money alone.
I do find their website a little confusing, but this is the membership you need:
https://www.avidog.com/shop/dog-breeder-memberships/avidog-breeder-college-membership-monthly/ Then be sure to join their FB group to ask there.