That Ena was not Alfonso's first choice was not surprising, given her status: it wasn't just his mother who didn't initially favor her as the next queen of Spain. Patsy was a fully royal princess who posed no risk of carrying the hemophilic gene, and who (in my view) was the prettier of the two. She virtually had the Spanish crown handed to her on a platter: all she had to do was reach and take it. But for various reasons, the answer was "no".

I didn't know as much about the situation with Baby Bee: it seems, then, that Ena was actually the THIRD choice of bride -- pushed on Alfonso as a consolation prize, because those he preferred rejected him.

The situation was not much different from that of May of Teck, the morganaut princess who got pushed on Prince Albert Victor, Duke of Connaught, for reasons that the other suitors (cousin Alix of Hesse-Darmstadt, Princess Hélène of Orléans) didn't work out for him. She got handed down to his younger brother, whose first love interest also lay elsewhere: but Missy of Edinburgh turned him down in favor of the future King Ferdinand of Romania (thanks to her mother's influence).