As everyone in Medieval Europe should know, following your choice isn't exactly the smartest movrt ever. Liz lived through the WotR and saw the shitstorm her parents' marriage caused, would she really want her son marrying an Englishwoman with an inappropriate pedigree (and yes I know she's a Duke's granddaughter, said duke is also local) for a king, the same way her father did? As they say, history repeats itself and the signs are all there. I think Liz would try to prevent that if she can do it.