I adopted her and realised she is pregnant,what do I do? will pregnancy stunt her growth?

Do you know how far along she is?

At 7 months she is way too young to have puppies of her own. If you can, a spay and abort would be the best option.

There are risks with every pregnancy, but the younger the dog is, the more risks associated with the pregnancy, not only to the puppies but to the mom as well.

If you continue with the pregnancy keep in close contact with your vet. Put money aside for any foreseeable emergency. She may need a C-section, or other help giving birth to the puppies.

Invest in a whelping box and heat lamp for when the puppies are born.

Put money aside for shots for all the puppies. They will need their first set before they're adopted out. Realize that puppies cannot be adopted out until at least 8 weeks of age, 12 is better.

She may not be able to or willing to nurse the puppies once they're born. Make sure you put money aside for puppy formula and bottles in case that happens.

Having a litter is a great expense, especially if things go wrong.

I would schedule an appointment with your vet, see if a spay/abort can be done. That's up to you though.

What will happen, you will get her spayed right now.
She is nowhere near old enough to manage a litter and yes it can cause permanent damage.

Shaz and Altenweg have given you the best options.

I would also contact the person/group you adopted her from and find out what you can about her history such as what dogs could have impregnated her (IF a spay/abort is not possible, you really need to have an idea of how big the father is to have an idea of how large the pups could be and if she could have been bred by her father or brothers). Let them know that any measures they have taken to keep females in heat separated from males is not working.

I wish both of you the best of luck and health.