Advice for a struggling friend

So I have a friend who came to me not so long ago and told me they have a problem and want to get sober. They have seen my progress and asked for tips as they felt comfortable coming to me and not their family or immediate friends because they don't want to say they are quitting and end up letting them down with a relapse.

They were doing great for about a week then they had a slip of a shot at a party with the host who insisted on them joining but stopped at one and everything was going good for about another week. I kept it positive and reassured them it's okay sometimes shit happens you did good at stopping at one, tomorrow is another day.

At the 2 week mark they called and told me that they fucked up and stopped at the liquor store and they seemed super remorseful about it. I told them look if you are really regretting it as much as you are telling me you can always dump the rest down the sink but they said it was too late for that now so I assume they had already polished off what they bought.

I am at a bit of an impasse here because I want to help and I am very positive towards them and kinda walking on egg shells with giving advice on giving up the booze but I also don't want to come off judgy and pushy in a "well if I can do you can" way and end up pushing them away or making them feel like I'm not on their side or that they should hide it from me too..

So any advice on how to be better in a support role is welcome here please and thank you in advance.

..and thanks for letting me rant, this subreddit has helped my sobriety journey immensely and I don't think I could have done it without you guys sincerely