Late self-employment registration; NIC and trading allowance

[jason13]

A friend of mine is a 19 year old student who started doing some tutorials to earn some money while at uni. She didn't register as self employed since her income is much less than the personal allowance.

1) She started giving tutorials in September 2017. I understand she should have registered as self-employed by 5 October. How likely is it that she'll get f
ined if she registers now? All her earnings (some tutorials and a summer job) are far below the personal allowance.

2) Can you pay NI class 2 if you're within the £1000 trading allowance? (I believe she was above last year, but not sure about this year).

[RMC]

a) She won't get fined if se registers now.
b) Yes.