Web Design Internship: Am I being exploited? Or should I continue to follow the promise of full-time employment?

[ZOO]

I have been doing it for a month for 2 days a week, 8am to 5pm and 10am to 5pm. Straight away my supervisor wanted me to design for clients, these banners for facebook company Pages. I got an email with their company and a list of clients. I get promises of getting a job after the internship because this company "is still growing", so I work hard, all the way through lunch to complete things, but she says I'm too slow and need to work faster. I get stuff to do like display advertisements to be designed at home to work on to Friday (I'm doing university full-time so I get pretty busy).
Last week she wanted me to design a full 1 page website for 3 clients of my list (just a mockup not coding using photoshop). She gave me a template related to their business, their "old" website and company photos and colors, and I need to redesign this template by taking screenshots of the page, putting the images together in photoshop then editing them. Some have sliders and topics that are irrelevant so I need to change the text, name ,writing, images, contact details, background etc. of the whole page. I am too slow and take 30min to design a full page even with extra tabs (which I have to recreate too). She says I'm much too slow and even when creating sliders that I shouldn't take so long and she gets angry at me...I feel very pressured to go there, but do it for another month with the hope of gaining a job...but I don't know...