The fact that she felt particularly tight, did not allow fingers and left you with a red ended cock is an indication that she was using the sponge method when she had the painters in.
I have had it happen to me a couple of times and the SPs confessed to using a sponge - the blood only showed up at the end.
One reason why I have given up RO - well almost, sometimes I cant help it but I do use a finger in deep to check conditions before I lap up any fanny batter. Years ago I encountered a sponge stuffer using this check.
Maybe one of the SPs on here could comment on the effectiveness of sponges? Should us punters avoid them?