The young woman has a sleeve style called a gigot or leg-o-mutton which dominated fashion early - late 1890's,she also has a pigeon breast blouse which did the same early 1900's.I have seen the gigot sleeve early 1900's & the pigeon breast blouse v.late 1890's but I've never seen the 2 together.The outfit is finished with hip-padding & a silk waist band.
Mother has a similar style sleeve but with lace edging which by this time was becoming increasingly popular as the price of lace came down but was more common in the early 1900's.
I would suggest the earliest this could be was 1897/8 & latest 1900.
I would think that if she'd just married she would be displaying her wedding ring.
Grandma appears to be in mourning as she has what appears to be crape banding around her cuffs.
jim