Sorry assumed you were a tradesman of sort, worried about ensuring you keep a customer happy and get the business.
Sometimes I wonder what people did before the internet existed, how did people previously make decisions about what is obviously the right thing to do??!!
Put yourself in her position, if you told someone that and they said nothing you'd think they were a bit of a c0ck! Or a normal salesman! If they said 'let me know if I can help' you'd think they were weird.
A polite e-mail empathising with her situation is so obvious I'm wondering whether you even deserve your monthly pay check!