Tenant got pit bull with out asking

[Justin Case]

A tenant of mine just informed me she got a pit bull puppy and did not ask permission. It states in my lease they need written permission.

The tenant is kinda slow and I could not understand what she was saying over the phone but it sounds like she is keeping it outside in the unfenced front yard.

What are my rights to deny a pit bull and how do I go about it since she did not ask and just got it? I would allow a dog up to 30lbs and thats it. Can I say that?

She is a great potential long term tenant and I do not want to
make her upset since she has a long rental history. Normally I would give notice to get rid of the dog or move out but considering the bad rental economy in the area and she is a good tenant I do not want to give an ultimatum and piss her family off.

Any suggestions?

Thanks.