i do think its cruel. society in the united states has made us act as though are child falling asleep on their own is somehow related to the parents "teaching", when in fact, sleep is a natural biological function that all humans perform. i am an advocate of cosleeping and there are many scientific studies to show the benefits of cosleeping. there arent the same studies to show sleeping alone is beneficial in anyway. my 3 1/2 yr old and 6 month old coslept/cosleep and have never cried themselves to sleep, nor have they ever cried when awakened as they feel secure with us here. you dont have to have your child cry, it doesnt teach them to sleep, rather teaches them that when they cry no one responds. it makes them so exhausted they pass out. i do not define that as teaching.
with daughter number one, we coslept. we rocked her as a baby, then around 1, we laid in bed together and i left when she was asleep. at 2, when she had an understanding, i would put her in bed after a book, and leave the room telling her i would be right back. she would fall asleep while i was out. then at 3, in her own room, i just tell her goodnight and she goes to sleep after playing in her bed awhile. i would suggest to you to get away from the rocking, and instead lay next to her, as thats much less draining and less to miss, overall, an easier transition.
also, i would focus on making sure there are no reasons she wakes up. try a white noise machine to see if that works, and put a bottle of water in her crib.
i would like to point out that the crying methods that doctors have suggested like ferber(who i dont agree with but..) were not intended for a parent to leave their child to cry for 45+ mins and they were definately not intended to cause a child to vomit. these things are cruel. the doctors originally had a detailed plan intended for a parent to start with 5 mins, check on the baby, then 10, ect. the parent was to acknowledge the baby with back rubbing, ect. these books people refer to never said just leave a baby alone in a room one night to scream for an hour, but time and time again i read that. if i were to cry for 45 mins hysterically, you better believe that i would pass out. the only thing taught is that no one came. please read up on the negative effects of crying it out. seroton levels, trust issues, crying more, ect.
as for selfish, my grandmother passed away last year at 93. i choose to do things that may not be easiest on me, but i feel are the best for my children. in the big picture, if i sacrifice 3 years of my life to not allow my child to cry, i will have 90 years of "me" time. they are this young for such short time. good luck to you, i hope you can find a balance for everyone.