Realise is a tangent, but is a pretty hefty one. Those words "do you take credit for it" imply (and this is IME a pretty universal view) that being 'bright' is 100%, unquestionably and with no faults at all, a GOOD. THING.
I am 'bright' although had car-crash of an upbringing (which could, in theory, knock out the 'nurture' bit), but was always surrounded by books.
IMHO being 'bright' - aka 'very clever' - really isn't a 'simply great trait to have and with NO downsides. I was 'bright' in primary school so kept being 'put up' years. Meant I did last year of Primary School 3 fucking times. Parents (who should never have been allowed to even breed) would then boast that their DD got 1/1/1 three years in a row.
Didn't ever mention that 'bright' cuts both ways, that their DD who got 1/1/1 three years in a row was ALSO bright enough to know the shit that was going on (not gonna go into detail other than was v def not pretty or nice).
Same now an adult. Have an IQ of 151 - yippeee!!! Not. It means NO-ONE can ever given me a 'surprise' gift (genuinely, have also fathomed it by their movements or odd words over the previous cpl weeks). Means have a BS radar like a forcefield (guess that's mainly good, but can sometimes be damaging).
Have 3 DS's, all are stupidly 'clever', but so so different to each other. One is in music business (but loathes 'business'); other is at Oxford (chucked in 11 GCSEs at A and 4 A-level with 3 at A and t'other 'just; an A); and third is just as 'bright' but feels dwarfed by the Oxford one (who also happens to be a total dude, really 'fit', and quick with a line).
I thing the sole thing I did for them was to teach them manners; ensure they grew to love books; and that they 'get' that they are really fucking lucky to have an educaiton which enables their 'brightness' to translate into whatever it is their passion is.
OP - I'd tell your friend to do one.
1: if she thinks 'bright' is genuinely 100% 'upside' only then she's as thick as shit (so thus cannot be 'credited' with DS's genius);
2: if she thinks his innate IQ is anything other than something which can be 'swung' up or down depending on opps and nurture; she is also as thick as shit,
In fact that IS my summary - your mate is at thick as shit and her DS's 'brightness' has got jack to do with her unless she has encouraged it to flourish via reading and, vitally, an understanding (a humility IYKWIM?) that not everyone is as intelligent as he may be is. Latter, given lame 'boasts' kinda suggest she's failed at that too.
Ergo, your friend is thick as shit and her kid happens to be bright would be my considered opinion
PS Another 'downside' of stupidly 'bright' - you can learn stuff absurdly quickly and which can make you look like a total twat. Witness post above which is product of fact I can type at over 100pm, but actually, genuinely does just make me look like a total twat for essay length post.
ENDS.