First thing, I would like to congratulate you for having such a
girlfriend. I think an understanding and mature girlfriend is what
most men(or just me) wishes to be with.
In some unfortunate one way relationship, one party is willing
to accept the other's flaw while the other can't. Extreme cases
could be one party sacrificing everything for the other, terms like
money, freedom, family, friends and dignity. These people can go to
the heavens or hell for their loved ones. And all they wish is the
other party be with them just as much TS would want her bf to reply
a sms. Thus resulting in over promise beyond their means and
capability.
Some would just want to save a trouble/quarrel knowing this would
just spell for future disasters. These people most likely already
prepared for a breakup, they just don't wan to pop the question so
that they won't seemed like the bad guy and gain some sympathy from
others.
Fortunately, mine's not that bad though she could be
unreasonable at times, but was worst last time. We had a few talks
with each other and have agreed to compromise to each other
demands. Our relationship was taken to greater heights from then
onwards. I think there must be some sort of give and take. Rather
than TS just asking to promise, she could have asked if her bf
minds anot. Like before asking your bf to buy a diamond for you,
would it be nicer if you ask or find out his financial capability?
It is meaningless for your bf to go bankrupt just to give you a
diamond so that you know that he loves you so much. Are you ready
to live a poor lifestyle with your bf if he does that?
He probably thinks smsing you each time he goes out is ridiculous.
With that kind of mindset, he'll never reply you as i guess he
promised you for the sake of keeping you happy and saving him a
torture from what you would do if he does not promise. Before
asking for a promise, let him understand the reasons behind it, for
men needs reasons to do things and i mean reasonable reasons. Not
reasons like you worry he might get involved in a car accident each
time he goes out because he seldom go out, this is
ridiculous.
1) you're not going to be of any help despite knowing. (he wouldn't
want you to know either, he would wish he could faster recover and
go back to you like nothing happened)
2) trust me, you won't want the things you worry to happen, you're
indirectly cursing him to get involved in an accident.
These are excessive care and needless concern. It's tying your guy
down. Frankly speaking, I think TS is being a liability to her bf.
Rather than being angry about him not replying your sms, trade for
something else. Like a shopping date/spree. That way, both of you
can spend time together, you don't need to worry about him in a
accident without you knowing, you're happy and he's sad for his
hole in the pocket for not replying your sms 
