given siobhan's national pride, i think philip's interest would soften her towards him but ultimately, she wouldn't trust him on a political scope -- it's nothing personal against him, of course, but she understands (in a general sense, in an idealized sense) how politics work & would thus be wary of him for ireland's sake.
more personally, i think she would like him and i think the idea of friendship isn't too far off? i think they'd be friends; if not, at least friendly. i think the fact he offered his condolences would definitely be something she remembered; while she was too fresh & new to really feel the loss herself, i think she would remember the act as something genuine and you know, those things matter. i definitely vote close friends!