wither, whither

Wither or wither means to shrivel up from lack of water, as of a plant--
If it doesn't rain soon, all the flowers will wither.
The plant will wither in this dry room.

Whither or whither ( rhymes with wither ) is an old-fashioned word meaning where--
"Whither goest thou?"
He went whither his fancy led him.

Now that you know that, you can say--
"Whither should we plant this flower, so that it may not wither in the sun?"

Note--"withers" may be the third person singular ( he, she, it ) form of "wither"--
If you don't water a plant, it withers.
"Withers" may also mean a part of a horse, sheep or cow, where the back meets the neck--
He measured the horse from hoof to withers.
Note # 2--"with her" ( two words ) means accompanied by ( with ) something or someone belonging to a female ( her )--
She went out to lunch with her mother.