I personally would do whatever works to make bedtime and naptime stress free, if she goes down easier feeding to sleep/rocking to sleep I'd do it. It won't be forever.
RIght on Kristin - great advice in your post!

I also have never heard of the magical 12 week mark and definitely agree with Michelle
Each child is different and learns to sleep in their own way and in their own time
I often fed my DD to sleep as we co-slept and it worked really well for us. I ended up running into an issue at the 6 month mark where she developed a sleep/breast association and would wake all night looking for a boob. Because of this I decided to end the feed to sleep system but it hasn't put me off using this settling method for other children I might be lucky enough to have . I have read many accounts from women on this site who said that they happily fed to sleep until their toddler gave it up themselves. Sounds good to me!

Have faith in what feels right for you and enjoy your gorgeous little buddha enjoying you!