Yes, ummm, the cousin may be right.Can't bank on them dropping it, but a s20 wounding is a possibility if only because the prosecution will hope to cop a plea of guilty to it and avoid a trial on the s18. That's why Siany needs a lawyer who will find out what the complainant has said in his statement(s) and what the other evidence is. Apart from the complainant being a) apparently drunk b) possibly friendly towards Siany, or not holding any lasting animosity towards her before any trial c) likely not to be clear in his recollection, if indeed he has any material recollection d) on Siany's account the original assailant on her, we have a suspect who herself says she can't remember how the man got cut. The lawyer might well think that any charge of assault is worth putting the prosecution to proof on, on that basis alone, because he may feel its his duty to do that, seeing as she can't remember the key part of events. He's got no instructions from her on that, of course, so he's in the dark. If , put to proof, the prosecution evidence given at the trial before the jury is absolutely overwhelming, then counsel can reconsider and advise appropriately whether a change of plea, and to what count, should be then made. At present, on what we are told, the prosecution case doesn't sound great, but we aren't in a position to say definitively. Only her solicitor and counsel can do that ,and she must be aided by a solicitor as soon as possible.
In the meantime, Siany, don't worry but get a solicitor!