Georgette, I wish that you had mentioned her previous experiences with heart caths. They are using different types of seals now, and I have heard of one case where they used a cardio or angio seal which came loose and went to the lower leg. One or both of these are collagen "plugs" which actually remain in place on the outer wall or puncture made by the cath sheath for quite some time.
I could feel a tiny lump in the area after my last cath in September, but I did not monkey with it.... Upon discharge, they gave me a "registration" type card with a serial number and lot number that came from the manufacturer, Cardioseal I believe (Cleveland Clinic).
The case I read about required surgery to remove the "plug" which had stopped blood flow going to the lower leg, thank goodness, instead of the other way. The pressure you mentioned that your Mother felt sounds suspicious, but if the seal had broke loose, she would already have been to the ER (it seems).
I would still keep an eye out for discoloration and of course pain in her leg. You never know nowadays.
Good luck to your Mom and yourself
Happy New Year