The answer to your question turns on that hardy perennial favorite dilemma: aggregation versus derivation. The 'intermediate-ness' of the intermediate library doesn't matter. The reason it doesn't matter is that the question is asked about the work, as a whole. I do not believe that anyone thinks that the precise order and arrangement of the call graph is important; what matters is what people think about dynamic linking. From the standpoint of, well,
ldd, the EUPL library is linked into your work. Either that triggers obligations or it doesn't.
Thus, what matter is what (a) the copyright holder, and (b) a court, thinks of this. The FSF, authors of the GPL, see all dynamic linking as resulting in a derived work and thus source distribution obligations. What do the authors of the EUPL think?
If you believe Wikipedia, the dynamic linking situation of the EUPL is completely up in the air, subject to the legal breezes of each individual jurisdiction. So we have even less 'principle' to apply to predicting the legal view of dynamic linkage with an EUPL license than we do with the GPL.
Really, your best best is to ask the copyright holder of the library for her or his view of dynamic linkage. If the copyright holder gives you permission, you're good. If not, whatever anyone else thinks of the EUPL and dynamic linkage, you might be on the wrong end of a legal action.