You have this piece right in front of you, and you want her to be thinking sex. So why not have her? If you think hard, you can probably think of a reason, but why should you think hard?

1st you need to think about getting her dress off, not a hard task, tho the sign of those ample hips is rather hardening. Just a couple of yanks and she is nearly in full naked glory. And a quick yank and your glory is out and ready for action.

She stiffens as you place your pole in position, but there is very little she can do to slow you down, much less stop you. A hand grabs each of her hips and then you thrust your hips forward. Hey, she is, er... was, a virgin! All the better for you.
As you continue to thrust, you see that Lizzy is using her tongue to caress the girl's rack. She ought to be really enjoying herself, if she forgets her upcoming fate as food of course.
That seems to be on her mind a lot as she resists your combined efforts. But she can't continue to resist. Each lick and each stroke stimulates her and builds toward an explosion. Not that you mind the delay. Your own pleasure is more important anyway, and you finish for the 2nd time before she finally climaxes.
She's a fighter. Most lasses give up about now and slide on in, but this one is still struggling as Lizzy slides over that flat belly and onto her hips. But her efforts are wasted. So to center them on something beneficial to her, you pull her hands onto her cunt and start them stroking as Lizzy reaches her vitals.
It doesn't stop her fighting, but she finds your suggestion a good idea and she is stroking herself vigorously as her bottom goes out of sight. Her legs now are slurped down, tho they kick vigorously when she comes once again. You slip off her shoes and her feet vanish into Lizzy.

You feel like celebrating and start towards Lizzy, only to have her hold up her hand and say "No".

"But..."

"I got pregnant because last time you did both of us. You want to raise twins?"

"No, but..."

"Maybe it's not the same thing, but why take the chance? You are going to have to wait until she is properly digested."