SIL Demands My High Chair Mid-Meal

SIL wants to kick off my toddler to feed her baby in MY high chair WHILE mines still eating.

I keep a small floor seat with a tray at my in laws (1.5hr away) to feed my kids (I bought it

for my son who's now outgrown it and my daughter 18months now uses it) whenever we

visit. Now my SIL uses it to feed her 11month old when she visits her mom's (every

week) which is no problem when we aren't there. However there's a second floor seat

with a tray that's in the basement that her sister recently bought but she insists

on using mine (?). Even when i was visiting she just takes it to feed her son meanwhile

I'm looking for a place to put my crying daughter who's hungry to eat and is older