verynaiceham your friend sounds like a total bitch.
"I ignore the digs as we are in a friendship group and don’t want to make it awkward for anyone else."
Please star thinking of yourself and stop putting others ahead of yourself.
"It’s the fact that she offers me advice me about things that she also has issues with. She has humiliated me before in front of a full table of friends when talking about my acne and basically said it’s because of poor hygiene standards when in actual fact her skin is probably worse than mine (just covered up with make up)."
If she makes any cruel comments decide how to respond. I'd go a total blanket ban on that topic. "I know you mean well, but I don't want to talk about it." That makes it very clear you don't want to discuss your skin, clothes or weight. If she persists she will look like the bitch.
Sarky comments, snide remarks etc (from you) will look passive aggressive. This is he best way, IMHO to shut her down. Tempting as it may be to give her a mouthful in private I would continue the same treatment if she tried to discuss this in private with you.
Then you know if she ever accuses you of saying anything inappropriate to her (especially to another in the group) you can honestly say, something like, "I decided 'a long time ago/back in October/back in 2017' not to discuss skin/clothes/weight/looks exactly because I found her/your comments to me hurtful, so I know I never said anything of the sort.
" She has humiliated me time after time and I’ve had enough." It's good you feel angry now and want to stop her doing this. Try your hardest to not sit anywhere near her on the bigger meet ups. Avoid getting into conversations with her. Nothing snide, nothing horrible. Just keep out or her way and enjoy your other friendships.