Likely in this case. I just wonder what position they started from...looking for evidence to support the particular hypotheses, or were they open minded about it...

That seems very clear from the article. She looked at it because the Louvre asked her whether that painting had ever been looked at in depth before. It seems that she didn't start out with any hypothesis about the history of this painting (other than what is probably the default assumption and what the painting was cataloged as, that it’s a 500 year old anonymous copy).

I find the parent's quote misleading without the context.

"Just the first pictures were enough for her to conclude that the two paintings had been produced in tandem. After that, it was just a question of watching the evidence pile up." is a quote that seems more appropriate to me.

Yes, confirmation bias still applies, but there's no evidence in the article that suggests a hypothesis to her work was established before she did took the first set of infrared images