I had the easiest time nursing in a cradle hold in my ring slings, because they are infinitely adjustable, kwim? I used my Maya for nursing in a cradle hold. I'm not sure if that would be snug enough for what you are looking for. Once they have good head control you can face them out, but a maya isn't going to give a lot of head control for facing out with a 3.5 month old most likely.
I never had a ton of luck nursing in a moby or wrap but maybe others have had good luck with that. I have a Baby K'tan to try out with baby #3 but haven't gotten to try that with a nursing newborn yet. You can do a cradle hold and have baby facing out w/ the K'tan, but I'm not sure if it would be as adjustable to have baby at *just* the right height (like you can do with a ring sling). There's also the stretch factor...great for holding them in and snug, but you may find that as the wrap or K'tan starts stretching out after a few mins/hours of wearing it may have her too low, kwim?
Mama to DS-2004
DD-2006
and a new addition-ds born march 2010