Obviously too much pressure may engender the explosion, if you got pissed off by your mother's behavior I say that this is a natural psychological reaction, you need space and time to deal with your stuff, with community outside, and everything,
But please don't go too far! Don't let yourself gets drifted away by your reaction, u may tell your mom words could hurt her and make her bleeding inside in silence,
Try to explain to her that your are grown, and that you are doing your best to reconcile between her and your schedule,
Try to approach to her to make sure that she doesn't suffer from any health issue or mental one,
May be she has problems!
Some mothers they said that the only thing that they regret in life is that tmore have kids, they steal time from them! Kids they deny them from so much fun in life! They even wished death to their kids!!
Some mother's they sacrificed all their life all their beauty to raise their kids, and they feel jealous when their kids spend more time with something or someone...
Don't say that you miss your dog more than her,
Be a good reason for her smile, make her always shining, choose always your last words with her, some meetings could be the last ones,
Remember always that the only person that deserves a special place in your life is someone that never made you feel like you were an option in theirs, and remember that the things you take for granted, someone else is desperately praying for!