Fraid not. While I was doing it I did actually think 'is that too thin' but then as it was only for a bit of colour for the glitter to sit on I didn't think it needed 2 coats, plus I thought that because I do a coat of zillionaire on top of of the glitter too that it may be too thick and peel if there were lots of layers!?
She did say she doesn't mind paying again which makes me think she may have meddled with them a little otherwise I would have thought she'd expect them for free if she's not done anything wrong? I do see that I've not gone right to the nail wall on the thumb and a little too far over on others! So it could be a bit of both xx
This is the attitude that will make you achieve your dreams and goals of being a great nail tech.
The bit where you admit that you didn't apply the product as well as you should have, is great because it shows you see your wrong doings and can try to improve them.
I'm not a Shellac user, I use Polish Pro from NSI and I have a client who drives me buts because she comes back with nails looking like this clients broken nail....why? because she does nothing to treat her nails with care and thinks they are tools and this is all happening with a short free edge.
So in regards to the crack, it's exactly that, a crack/split where the client has knocked it hard against something and it has split.
I will also say that in your original pic, your application is not crash hot (but you see this for yourself anyway) and although some clients nails do grow very fast and can possibly have a lot of re-growth after one week, this looks more like that the product has worn away (maybe even been filed slightly by client) and it's possible because you are not taking the product up far enough (but with still leaving a small margin) you might not be actually sealing the color coats with the top coat, which in turn will wear the color/product away quickly and cause lifting/peeling.
You need to leave enough of a teeny margin for the color coats so that when you apply the top coat it actually slightly goes over the color edge and seals in the entire color coats.
I know this is easier said than done but with practice, you will get there.
I too question if this client has not either filed away her top coat as the 2nd pic does look dull or she has played with chemicals that have taken the shine away, either way, this is definitely a client issue, not a Shellac issue and it sounds like your client knows it by not arguing about having to pay for a re-application of her Shellac service.
Let us know how things went when she came in