I think you might be expceting to much if you think your baby will behave the same way day after day at 3 months old - they change so much, go through growth spurts, learn different skills and have stuff going through their amazing little minds - just because she falls asleep easily one day really doesnt mean she will do the next...
as they get older they become more predictable..but even at 16 months, my son who sleeps through the night mostly will wake up if he is teething or has had a busy day and is over stimulated.....
lots of people don't feel comfortable with CC at this age - but, you are the mum and if you go with your instinct and make sure you aren't setting unrealistic expectations, then Im sure a little bit of crying while settling is no bad thing. Personally I did a lot of sling based naps / walking in the buggy - and then at about 3 months used a dummy/ pick up put down to get ds to sleep in a cot...I didnt actually leave him to cry at all until about 7 months when I did sit with him patting/ singing next to the cot to teach him to fall asleep - but he was a really really bad sleeper, waking many many times a night and my sanity was nearly gone!
it worked very well .....I think - personally (and everyone will feel different) - that babies cry while falling asleep because they are tired, and if you can get them used to the cot or crib without letting them cry too much, then it will be all the better for their sleep
I really disagree with the poster who says 'wait a couple of years' - an older baby will be absolutely fine having a bit of a shout / roll about while falling asleep ....I can't imagine feeding or cuddling a baby to sleep for 2 years - but , its personal and if you dont mind doing it, then obviously its a lovely thing to do!
so just try to roll with it a little...good luck!