Inheriting work and Intellectual Property Rights

Hi, I'm relatively new to freelancing, having worked in-house for a number of years. I have worked on a few projects for new businesses, mostly creating marketing materials and social media posts. A new client of mine has asked me to work on some artwork, the query I have is, they used to use a chap for their design work, from what I can gather she no longer wants to use him. He designed some characters for her business which she wishes to use and a mock up to the artwork proposed. She wants me to now design this item and has asked for 'something similar', she has only provided .png files which has rung alarm bells as to whether she has the IPR on this.
I have broached the subject saying that ideally I'll need vectors and that she should perhaps have a conversation with the previous designer around IPR but I gather she doesn't want to do this atm. I think I'm going to have to ask her to refer to her original contract with the designer to ascertain whether she has the IPR on the works or not before I engage on the project as I don't want to leave myself open to problems later down the line. Has anyone else experienced something similar? I really want the work but need to protect myself from any infringement risk.
Any advice gratefully received. Thanks