Why some mothers and MiLs seem to think that their grandchild is an extension of themselves, so can do what they like , is really beyond me - it just shows a lack of respect, however close they are to either DS or DiL!
This woman sounds like a complete nightmare. To barge into the delivery room, bringing a complete stranger with her and take photos is unforgiveable - I'd be very tempted to make a complaint to the hospital about it.
She is obviously thrilled to be a grannie, with the posting of photos and dragging her friends in uninvited, but you have the right to bring up your child as you want, without anyone's input, so stick to your guns! Close your curtains - in fact, if I saw her peering through the window, I'd close the curtains in her face - if she complains either directly or indirectly via your OH, you can always say that as you were walking around in your robe/ breastfeeding/ getting baby dressed, that with people out on their constitutionals, you wanted a bit of privacy as you never knew who would be looking through the window!!! (If you shut the curtains in her face, say the sun was in the babies eyes!!)