In-law Driving Me INSANE!!!

My boyfriend's mother claims that she means we'll when she's constantly offering up advice on nearly everything in my life...including her own son. She's one of those know-it-all types who needs to be the expert on EVERYTHING, even if she has to interrupt you rudely to say, "No, now listen to me...". She's constantly trying to make everything about her, even when my boyfriend's fellow Marine and friend died recently. She ran right onto Facebook and started posting about it, before the victim's wife even revealed to anyone outside the unit that her husband had died! I'm up to my eyeballs with annoyance at this point, but my boyfriend keeps making excuses for her, like "Maybe you misunderstood what she was saying". Ugh, NO, I'm not...she's just an attention-seeker from Hell and I'm ready to go nuts!