Please do not declaw your cat. Claws are extensions of their toes and the last joint is removed. It can very easily go wrong, get infected, impair movement and some indications in some cats are that it causes lasting pain. Forever.
If you friend means training not to scratch your furniture, well yeah, maybe so, they have no means to scratch without claws.
However it's a pretty easy thing to provide scratching posts in a couple of places in your house and encourage your cat to use them by playing on them, rubbing catnip on them, rubbing her feet on them in a scratching motion.
Some cats like vertical scratching posts, some prefer horizontal. No loop carpet works (their little hooks can get caught in the loops and put them off) and the jute backing on carpet works. Mine have a couple of pieces of soft cedar from the ends of split rail fencing that they love the best. I do have a bit of maintenance with the cedar as the cats scratching leaves little piles of shredded cedar around the log, vacuum before people come to visit.
Other training might actually be impeded by declawing. If the cat's toes hurt she might be reluctant to scratch in her litter.
PLEASE don't declaw. A Vet who will consent to declaw for you should be viewed with much alarm, it's not in the cat's best interest.