That's why I used the modifier 'vanishingly' to convey that zero is very much included in the range of possibility, which isn't really weird when something is extremely improbable.
Side effects are largely what they are for most vaccines: fever, muscle ache, headache, fatigue, injection site pain, redness, and swelling. All can lead to hives, rashes, swelling, and in extreme cases anaphylaxis if allergic to the vaccine or its contents.
None have cutaneous thrombosis specifically, or blood clotting disorders generally, as possible side effects. Medscape lists no interactions between these vaccines, an October 2016 clinical study ( https://pubmed.ncbi.nlm.nih.gov/27780630 ) showed no adverse effects or statistical difference between administering them together or apart, and there are no contraindications for the immunocompromised - quite the opposite, in fact, which is why she received them alongside the transfusion.
What does have thrombosis listed as a very likely side effect? Platelet transfusions ( https://www.ncbi.nlm.nih.gov/books/NBK560632 ).