I think your a great friend for trying to help, and I find I get really excited about breastfeeding and come off a little strong. I love talking about it, and I really wish everyone could have the great experience i have had, and am still having.
However I know a new Mum is dealing with a lot! The best way to help is let them know you are there if and when they need it. I go to Le Leche League meetings, and I have a few brochures (i write info on how they can easily find meeting dates on the brochure, for example the facebook page of the local group), and tell them i would love to go with them if they ever wanted too.
I think its really important for new Mums to know they have a friend to go too if they need help, however, my SIL came off really strong when my LO was new. I had lots of issues and she had all the "right" answers, when in fact she had no idea what was going on and I found it really frustrating. She ended up making me quite upset with all her unsolicited advice that really was not relevent. Whereas my cousin (who is a Le Leche League leader) was very supportive, she didn't tell me what to do. She strictly supported me, encouraged me, and answered my questions when I asked. I still go to her for advice.