Ok, so here's my first full-fledged lesson in sonnet writing (everything up to this point has just been core, starting principles).
When you've ended a line with a particular word, consult a rhyming dictionary to see what other words you will have available for the line that will rhyme with that one. In the case of "manner" Zkribbler has given us the options:
banner, branner, canner, danner, hanner, kanner, manor, planner, sanner, scanner, spanner, tanner
When it is very few, like this, that's a potential danger sign: that you will have to distort the meaning of your second line in order to have it end with one of these words. You can run through them one by one. Does your subject give you any pretext for talking about canners or scanners? Does Sarah live in a manor? what even
is a kanner or a hanner?
Before you get too invested in composing that follow-up line, don't even bother if the possibilities are so limited. Move back to the first of the lines and revise it so that it ends with a different sound.
This involves the deepest principle of sonnet writing, as I've suggested before: being willing to revise lines. You throw away a dozen lines for every one you keep. Becoming an experienced sonnet-writer just involves getting quicker at these throwaways.
I'll give you an example from my sonnet. I've said I want to write a sonnet about the battles between MRAs and SJWs on this site. But my imagined audience is someone who doesn't know the site, so I have to start the sonnet by introducing them. So I've got an idea for two possibilities for a first line:
Because the internet has everything/serves every niche. . .
(. . . it has a site for fans of the Civilization series of computer games . . . and on that site there's a forum for discussion of non-game related topics . . . and on that forum a certain kind of thread comes up . . .)
I like the thought "serves every niche" better than "has everything" but I know my rhymes for niche are limited: quiche, fiche. So I'm not even bothering to progress in my composition until I get a different way of stating my lead-in that's a little less flat-footed than "has everything" and has more rhyme possibilities than "serves every niche."
So think of an alternate way of discussing her manner.
Also, you're shifting away from your core thought "I don't know whether you've ever received a sonnet before [because, in part, of stated qualities]" and being drawn in by the gravitational pull of S's 18th.