honestly silena is not scientifically minded enough to follow that lead, she would assume that it having been tested before meant it didn't need to be tested again so going with her ignorance on that matter is easier to keep her interested.

she might have gotten antsy enough to try to seek out someone to test the drugs though, maybe via schmoozing some of the guests at caroline's gala. she was working waitstaff, effectively invisible in that respect, but maybe she could have eavesdropped enough to find prospective people to ply with chocolates and pastries etc in an effort to curry favor and get access to lab tours or whatever in order to see which lab is capable of the tests? that way she could have something to contribute.