[...]Relative size/build, and disabilities leading a greater perceived risk is mentioned.
Edit: Basically you have to convince the jury you used reasonable force.
Worth keeping in mind that acquiring or carrying an object for the purposes of self defence is a crime in the UK. You can use objects as weapons, but there has to be an everyday reason for it to have been within reach.
There is a complication with that. Women in (arguably, and thus argued) spousal assault situations are far more likely to kill/injure their abusers with a knife (a household one), which is often taken as an aggrevating factor in any case even if determined to be a defensive/provoked act after years of physical/psychological abuse have come to a head. Overwhelmingly, a man who kills/injures a woman does this with just bare hands/etc and thus (even if the definite aggressor) may not suffer the same 'upgrade' of penalty when convicted.
There's talk at the moment of how this isn't quite right (hard to work out what's truly just without making 'metajudgements', every case is of course a special case and liable to interpretation[1] in getting to the truth of the matter) because physical bias begets an inequality of judicial treatment by way of the 'necessary' choice of weapon.
(And, no, this is not to bring us back to "but if everyone had a suitable gun, it's be equal again" argument.)
Obviously household knives (rather than 'zombie knives') are going to be accounted for as more everyday defensive objects, but it still holds a sway. And the answer is not "every woman can get away with stabbing any man, on basic principle", either, which (not just as a man myself, I hope) I think is rebalancing too far.
[1] A recent one had a long-term wife, in a marriage of good social standing, pleading psychological control and 'snapping', even/especially with an actual calm "I'm glad I stabbed him, in the heart he hasn't got" statement spoken to the bodycammed police as they arrived, which I presumed would end up being dealt at least leniently with from the reported claims, but the court (which I would trust to have a better grasp of all salient details) seem to have found her to be the instigator/aggressor in this case, and not in the bad-old-days way of "He was a respected member of the community, so she
must be mad!" way. Possibly appeals/campaigns will follow. Possibly it
was a travesty of justice, but right now the judgement is as it is, whatever the trend is in general on these rather complicated matters. So, right now, it seems that it was her that went 'straight to deadly' (over an argument involving a meal) rather than with another case with an oft-punched/strangled/etc girlfriend in a grossly unequal partnership who scrabbled for a kitchen knife as the violent boyfriend goads her and tells her she won't dare do it (or claimed/reported as such, of course) just before she finally did. (This latter case being challenged, because the aggrevating knife seems to be the main reason it went into custodial territory, so from being trapped in a relationship to being trapped in a cell.)