Right I'm back
Of course the toy gun and the nail was not safe, but it's nothing compared to a child who say, is punching you daily or grabbing a knife and going at you with it. The incident in foster care was obviously after her leaving their home and was very serious
I have a lot of sympathy for the mum being frustrated by those constant small things. Big things sound scary, but I've found that sometimes it's little things which can get to you more than the big things.
Also, I seem to remember that Alex was a child who rarely lost control. The mum was shocked when she once actually screamed and raged, and this was quite a while after homecoming. Some children rage and tantrum frequently, but others...don't. I mean, we're talking about a 5 year old here who nearly NEVER tantrums about anything, and has a lot of control over her outward behaviour, whatever she is feeling on the inside. On top of that, some of her behaviour I would describe as passive-aggressive. Put it together and it says quite a bit about her and it does indicate emotional issues which are more than mild.
I'm honestly very glad that both my daughters tend to be tantrummers and ragers and show their anger, rather than keeping it locked away and being passive aggressive
That's not to say they never do it. I remember DD1, a few months after coming home, started to spill her drinks. On the sofa's and objects that stained of course. She insisted sweetly that it was an accident. And did it nearly every day. She would go, eg. 'oops Lilka I'm sorry, I spilled my ribena, look, what should I do?'. And she was smirking at me. When I complained to my mum and a friend they BOTH said 'ah, she's almost certainly just clumsy, don't be angry with her', 'she's apologising and everything, it's just an accident', 'I'm sure she isn't smirking, and if she is it's a nervous smirk because she's scared you'll be angry with her'. One day she did it at my mum's house. 'Granny X, I spilled my orange juice on your sofa, I'm so so sorry'. Granny told her how clumsy she was at her age. When granny turned her back, DD turned to me and smirked with raised brows while swilling her drink in her glass and making tipping motions
In-bloody-furiating
I didn't say anything to granny, because I knew full well that it would be me written off as silly, fussy, reading things into it that don't exist, being unfair to poor DD, and as someone who just doesn't understand how kids can be - understandably of course, I'm only a new adopter of course, it's not like I can be expected to get how kids are, given me time, I'll 'get it'.
A while back, now adult DD says 'oh Lilka, I used to do things that wound you up because it made me feel good, I remember when I x and y and deliberately poured my drinks everywhere on purpose and pretended it was an accident. Do you remember?'
Do I heck 
Anyway, the point is, I suspect several of the thing Alex was doing were exactly the same kind of thing - she knew it wound her mum up if she did x, so she did it repeatedly. And maybe it seems odd to be wound up over something small, but you can get bogged down in the little things really easily, especially when you don't have a clue why it's happening