Dirty trick, but illegal?

[Four Seam]

ASA or NFHS rule set, tournament play. While in position as third base coach, I found that whenever we had a runner on first base, the big first baseman would move to a position between me and my base runner so she could not see my signs. As I moved closer or farther from home plate to get a better angle and my base runner stretched to see me as far as she could and still keep a foot on the bag, the first baseman would move accordingly, obviously to keep blocking the view. This delayed the game because my batter would not get set to receive a pitch while I was trying to give signs. In the actual game, I settled for letting our first base coach relay the signs to the base runners, even though this was a disadvantage. Question is, in this situation, if coach had asked for time and complained about this practice, would you as umpire have taken any action, possibly under UC or delay of game rules? Thanks for replies.