I always find perfume is a safe choice or a gift voucher for a department store where they have lots of options to purchase something they want.
Good luck!
If you are a really great cook, make her brunch lunch or dinner. If you cant cook then take out from a restaruant as many are doing take away now.
Could be hard if you are in a covid hot spot with everything closed. Maybe go around and do a days gardening for her. Maybe she said she needs something for the kitchen garden or house that you could get for her.