If this large amount of discharge was either vomit or a loose stool, the yellow color of part of it may indicate a problem with her liver. Babette is quite overweight, at 30 lbs. and this can be the source of certain medical conditions, especially in senior cats, like diabetes, liver or kidney problems.
You might want to make a change to her food, to keep her more healthy, if she is not currently eating high quality canned food that is grain-free. Here is an excellent article written by a feline vet about the best way to feed our cats:
There's also a possibility that this discharge could be from her anal glands, indicating that the fluid within may be infected or impacted.
I'm glad that she seems to be eating, drinking and pottying normally and is talkative, as usual; however, a complete, in-person physical, including a routine senior blood test and urinalysis at her vet's, would be a good idea, to make sure all is well. If you can, bring a sample of the substance you found on her cat bed with you, to the vet's office, for analysis.
I hope all will be well with Babette!
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