The visitors got off to a flying start as Claudia Pina converted from the spot to hand them an early goal after just two minutes of action.
However, Santiso s ladies were also gifted their own penalty and Paula Fernandez fired home to level matters 10 minutes later.
With the score 1-1 heading into the half-time break, the hosts found a breakthrough to gain a late lead when Teresa Morato struck deep inside injury time off a fantastic assist from Patricia Hidalgo.
After the restart, Rayo kept their nerves to defend their narrow lead until Sheila Garcia compounded the visitors woes when she struck a third of the match in the 78th minute.