I made a mistake she is a pup. Will she get sunburned and how long can I keep her in the water

Ahh OK, I misunderstood your other post.

3 1/2 months is probably a little young to let her go swimming.
You need to wait until all her muscles and bones develop properly before doing too much strenuous exercise :)

Yes, dog's so get sunburnt but white dogs are more prone to it.
I'm assuming your min pin is either brown or black?

If you are concerned there are doggy sunscreens available, just rub some onto her nose and ears or anywhere else where skin is showing :)

Ditto on the misunderstanding. Sorry, puppy! Yeah, 3 - 4 months doesn't need to go in over her head, but she can start learning in a wading pool or washtub or even a bathtub. She'll sunburn as fast as you do, so don't do sunscreen and she'll be fine.