I KNow tis is kind of off topic but i need some advice from experienced web developers and business people.

ive recently come across a issue , i developed a website for a client, its been a few months ans the client cant seem to make u her mind in what she wants for her website. I offered advice as a have a decent knowledge of SEO , social marketing and all the rest ( you kind of have to when you are competing in serps for web design queries because all of your competition knows seo too ).

Anyway she enlisted the services of a content writer , i went and looked up the site of this person , a WordPress site ,not even fully responsive , using a yoast plugin.

I phoned her since we were now to collaborate , i had no issue with this but over the phone she told me i need to supply her links of my work, so she can see if i can work with her !!! i was insulted. I need to prove myself to somebody who clearly doesnt know what they are doing. My seo and content is far Superior to hers , the site i had created for my client has Superior structure and ranking than this "Seo Content Writer" site.

She then told me hat if she uses another developer my footer credits will be removed , fortunately this woman never paid in full for her website and i am now going to decline the rest and take the site back as i have 3 clients waiting for websites.

My question is in future if somebody has paid in full can a content writer contract another developer and simply remove my copyright on the page? Because i have worked with one before and i know they sub contract to developers. Is there a clause i can add to my contract to protect me from this?