I'm commissioning a sexy audio and I want some /sci/ insight.

The script is going to be performed by an IRL MILF. Naturally, the audio's going to be me (19yr old boy) fucking and impregnating her without her family knowing it's mine.
>How would younger sperm interact with a mature egg?
I'm looking for notes and phrases for her to say, specifically regarding the biological fertilization aspect.

Like;
>Oh there's hundreds of millions! Swimming inside my womb~
>This could be my very last egg....please, give me your baby...
>Mix your teenage genes with my MILF DNA! Fuck yes!
>I've already had a few kids, my womb is already prepared to hold our little bastard...