It's hard to say exactly what you should do without knowing details, but I'd also say we shouldn't back away from pointing out sin in the lives of others that we care about. There are things which tell us to be sort out the sin in our own lives before picking fault with others, but that's more teaching us not to look down on others for their faults, but to look at ourselves first and sort ourselves out. So I don't think that's relevant in this case.
You do seem to care for the person and so any talking you'd do with them about this would be out of love for them and wanting to get things right, not only so the relationship between the two of you is OK, but that this person is able to deal with the sin in their life (which they may not even realise they have).
Matthew 18:15-17 says:
If your brother sins against you, go and show him his fault, just between the two of you. If he listens to you, you have won your brother over. But if he will not listen, take one or two others along, so that 'every matter may be established by the testimony of two or three witnesses.' If he refuses to listen to them, tell it to the church; and if he refuses to listen even to the church, treat him as you would a pagan or a tax collector.
Basically, don't shy away from helping someone identify sin in their life - do it to help them. But do it between the two of you first, so speak to your friend about the issue and try and sort it just between the two of you. If that doesn't work, and if it's appropriate, start to involve other people you both know to help them - but be open with your friend and say that you're going to try and involve some else. The thing to be careful here is that you certainly do things to help your friend, rather than make them feel bad and that is done most lovingly if you don't try to shame them or spread their sinful actions around so others know. So do as Jesus said here in Matthew and sort it between yourselves first, or then between a small group. An illustration of what not do here is in Genesis 9 where the first thing Ham did when he saw Noah's drunkeness and sin was not to help him, but to go tell others who knew Noah about the problems, shaming Noah further.
Hope you manage to get things sorted out easily and your friend listens to what you have to say. You need to speak them as much for their sake as your own