can i sue someone if they still own me money for business they bought from me?We have a contract said she must pay but now she doesn't want to pay

We have noterized contract stating she must pay me monthly for the business she bougth from me. We've been going through some misunderstandings and she said she isn't going to pay me anymore and she doesn't care if i have to take her to court. So I need some legal advice of what must i do with her. Thank you