Maybe I missed this minor detail, and this probably goes w/o saying, but since (according to the OP) she's flying in a cabin that gets her AA Arrivals Lounge Access she might as well wait inside, eh? If your flights end up not arriving as scheduled (a distinct possibility at LHR), then she'd be able to freshen up, get some breakfast, etc. And, if you're running late, or it's taking forever to transfer across LHR (another distinct possibility) you'd be able to either leave a msg. with the AA Premium Svcs. agent there.