Rectal bleeding

Emma, who is three, just emerged from her litter box meowing and trailing poop around the house. She appeared to be in pain. The poop had bright red blood in it and she had blood on her butt as well. We cleaned her up, scooped up some of the poop and put it in a Ziploc bag. Being New Year's, the only place that is open is the emergency vet services who said to keep an eye on her and if she acts funny, bring her in immediately. If not, calling our vet in the AM would be okay, too. After the incident, she had her usual after-pooping-funny-spell, a quick snack at her food bowl, and is now sleeping in her favorite spot. I checked her and she is not oozing blood. This has happened one other time about a year ago. What could this be?

I also wanted to add that she had a tapeworm a little over a year ago that caused a lot of throwing up. She puked the tapeworm up and was given medicine. She hasn't shown any signs of tapeworm since then.

We looked through the house and we see no signs of mice.

She does not eat any table food. Her diet has not changed.

It could be as simple as a little constipation, or hair passing. However, I would take the sample to the vet tomorrow for a good look to be safe.