[gemy]

If she is eliminating and eating well and no obvious signs of pain when you palpated her all over; my first goto would be resource guarding - you or her couch chair what-ever.
this is not that quick of a fix. But she must be Immediately Corrected. Taken off the couch or chair with a firm and clear NO. If she is snarling or snapping at your guests she is corrected and now you tether her to your waist if you want her to interact with your guests. Puts you into a position to immediately correct bad behaviour. Immediate is keyword here. Always couple the correction with a stern NO.

And btw periodically over the years you might have to re-instate the tethering or corrections. I know I do have to with my senior Yorkie who likes to slip back into resource guarding *me*.