I think it depends on your relationship with her.
If she's approachable and you're on good terms, she might love to hear " I norticed you got a betta! He's gorgeous! I have x number."
She'll talk about her fish for a while and ask you a little about yours then
After a little while say something like, " several of my friends have bettas that lived for over 5 years and stayed very healthy and they told me their secrets -- i could bring you a care sheet that I followed bc I had mine in a tank that was too cold -- they need heaters."
Prana (deep blue/purple CT female) Fluval Spec 2
Qi (turquoise CT female) 5 g riparium
Vanilla Beast (Ivory apple snail diffusa), Watson and Crick (Amano shrimp), Tributary (Moss Ball aka AquaTribble) Fluval Spec V
Pond and ramshorn snails (so many!) 2.5 g
Mr. And Mrs. Smith (assassin snails) 0.5 QT tank
Leopard ramshorns 16oz NPT Mason Jar