Hi, there,
I'm writing this quickly before my baby wakes up from her nap! SOrry if it is a little scattered.
I understand that it can be hard when someone is doing things so differently than you do, and thinking it is unsafe for a vulnerable little baby!
Let me reassure you, though. There is actually a lot of literature out there for how to safely sleep with one's baby. It's actually very safe, especially when done properly. Not only that, but it is very good for bonding, and for the baby's development. What you can do is encourage the good things your sister-in-law is doing, and give her information that helps her to do the things she does in the best possible way.
There is also a very widely respected school of thought that responding sensitively and immediately to baby's cries is very good for developing strong communication between parents and children. The cry-it-out approach, in this school of thought, is considered not only traumatic for the baby, but unnatural, and breaks down communication and makes discipline difficult later. I'm sure that loving parents have used it as part of an overall very caring approach to their children, and their children have been okay, in spite of this unfortunately well-marketed advice, but it is a tradition best left in the past.
The baby sleeping on his stomach isn't as dangerous as you think. It DOES increase the risk of SIDS, but it is only one factor in many. Sleeping with his mother reduces the SIDS risk because she is in effect acting as a respiratory pacemaker for him. The risk that she will smother him is almost non-existent. Mothers are very in-tune with their infants and don't roll over them unless they're drugged, have been drinking, or are extremely sleep-deprived.
WHat you can do, though, is encourage your SIL to put her son to sleep on his side. I think hwat she is intuiting is that babies experience a falling sensation because lying flat on their backs is so foreign to them, and by comparison to being upside-down and snugly-fit in the womb, flat and stretched out on their backs feels like falling. Putting him on his side is a safer and more comfortable compromise. Gently stretching out his bottom arm helps keep him from rolling over onto his stomach.
Speaking of the mother's health, she probably hasn't eaten in 2 days because she is so overwhelmed with caring for her baby! You can really score points and gain entry to her thought process by showing her some kindness. Make her some of her favorite, healthy food and offer it to her in a women-bonding type of way. Sit down and ask her how she's doing. Listen. That is a great way to get her to listen to YOU.
You do want to gently encourage her to breastfeed exclusively. Bottle feeding mixed in with breastfeeding severely undermines milk supply and can confuse the baby. Bottle feeding's also easier for the baby than breastfeeding, which takes a little muscle (and is therefore better or the baby).
As for developing negative feelings toward the baby: at first, the attachment parenting approach DOES take a lot of involvement. But that's how parenting goes. In the attachment approach, which is what your sister-in-law is more or less following (but needs more information about), the time/energy/attention commitment is invested earlier, and pays off later as the child is growing up feeling very secure in his parents' love, and becomes more independent, less clingy and better disciplined.
DO show sympathy for the hard work that parenting takes, and make sure that your brother is giving her breaks. Make sure to encourage him to be very involved: changing clothes and diapers, and helping with baths. Make sure that he is helping with food and keeping the house in order.
In the beginning, for all of us, of course parenting is very hard and overwhelming. It is hard to watch, and she will make her mistakes, but your SIL, being so close with her baby, has been learning about his needs at tremendous rates. Tell her that you think it's wonderful that she is being so caring and attentive to her baby's needs. We can all agree on that, and it's a great starting point to introducing some advice. But be willing to see that different parenting styles also have their merits! And she will more or less do best, for her baby, by following the ways that seem most natural to her, just as you have more or less done best, for your son, by doing what felt best to you.
So, again, what you can do is encourage your sister-in-law to learn *how* to respond to her son's cues, since, after all, it's not only hunger that will make him cry. (Gas is a big one, of course! Teach her the lubricated-thermometer-in-the-bum trick to relieve his pain.) You can also tell her that crying is a late feeding cue. Teach your sister-in-law about rooting behaviors that signal hungry before the baby gets frantic.
If it were me in your situation, I'd buy a cheap used copy of Dr. Sears' Attachment Parenting Book, and his Baby Book, on amazon.com. Dr. Sears is an extremely experienced and well-respected pediatrician, with 8 happy, healthy, successful children of his own! It sounds like your SIL WOULD listen to his advice, especially if you introduce it as information that really supports the natural instincts that your SIL is so brilliantly following on her own (the best way to reach your SIL is by showing her your respect for her obvious intense desire to care for her son instinctively, and not to knock the mistakes). Dr. Sears just fills in some of the gaps with his medical knowledge. Tell her that all of us mothers have our instincts, but there are just some things that instincts are a little vague on. Like that fantastic thermometer trick!!!
L.
PS about her staying in the house: some moms want to get out. Others LOVE their nest. I pretty much didn't get out beyond trips to the dr. for 2 months (still really don't get out much!), and i don't resent my baby. Your SIL is doing it her way. 10 days after birth, it's very normal to just want to be snug with baby. This could last a while, but don't put stress on her. *That* would be the emotionally unhealthy thing for her. Staying in holding and bonding with her baby is a good thing!