Two ring systems in different countries, need two different monitor subscriptions

I live in the USA and have a ring system for my home and have an alarm monitoring subscription. I recently installed a second system for my mother-in-law who lives in the UK. I am the owner of both systems (she does not have a cell phone so cannot access the app.) The UK trial subscription for home plan has just ended, I need to sign her system up, but can only add a US plan. Can I have two subscriptions in different countries? If so, how do I do it?