I've just been looking at the likely sentence for assisting an offender, and it depends on the crime the offender committed.
4Penalties for assisting offenders.
F1a relevant offence], any other person who, knowing or believing him to be guilty of the offence or of some [
F2other relevant offence], does without lawful authority or reasonable excuse any act with intent to impede his apprehension or prosecution shall be guilty of an offence.
F3(1A)In this section and section 5 below, “ relevant offence ” means—
F4a relevant offence] the jury are satisfied that the offence charged (or some other offence of which the accused might on that charge be found guilty) was committed, but find the accused not guilty of it, they may find him guilty of any offence under subsection (1) above of which they are satisfied that he is guilty in relation to the offence charged (or that other offence).
(3)A person committing an offence under subsection (1) above with intent to impede another person’s apprehension or prosecution shall on conviction on indictment be liable to imprisonment according to the gravity of the other person’s offence, as follows:—
(a)if that offence is one for which the sentence is fixed by law, he shall be liable to imprisonment for not more than ten years;
(b)if it is one for which a person (not previously convicted) may be sentenced to imprisonment for a term of fourteen years, he shall be liable to imprisonment for not more than seven years;
(c)if it is not one included above but is one for which a person (not previously convicted) may be sentenced to imprisonment for a term of ten years, he shall be liable to imprisonment for not more than five years;
(d)in any other case, he shall be liable to imprisonment for not more than three years.
Criminal Law Act 1967
Looks like 3 (a) to me - 10 years max. I wonder if she'll accept the mitigating circumstances put forward. It's not her first offence.