hi guys i just want to ask some opinions or experiences about this ...my daugther got a two passport one is philippines passport ,and a british passport .when we came in last september 12 she uses her philippines pasport so her arrival stamp is in her philippines passport

my problem is she got a visa going to riyadh for 3 months leaving on october 2nd and her visa is in her british passport and leaving the philippines using her british pasport .would they question me about it why is it that she doesnt have a arrival stamp on her british passport ?any views or advice what should i do when we leave?
Many thanks in advace