I can’t finger my girl for more than 5 minutes as she start trembling and crosses her thighs doesn’t allows me to finger her,instead asks to fuck her, what may be the reason behind it?

She just gets done with fingering very quickly I can feel that reaches her orgasm as she starts shaking and just can’t take it more, now I at the same time want to extend foreplay and don’t want to rush into piv but can’t as she suggest as she just wants to fuck rather then her getting fingered, how can I make the foreplay longer?