How to tell if a number has blocked your iPhone?

OK so this person I'm messaging has gone from imessage to text message (blue to green) within a week. I sent a few imessages to her but she didn't reply to any of them so I'm thinking she could've blocked my number without telling me. Is there a way to tell she blocked my iPhone without ringing her with caller ID on? When a user blocks a number using the iOS 7 feature does it still tell the blocked number that the imessage or text message was delivered/sent?

Are you new at stalking?

How is your message going to be delivered if your number is blocked?

A pro stalker would call or send a message from a different phone and see if that gets a response. Otherwise, her phone may just be off because she didn't pay her bill…

She may have just turned off iMessage and gone to traditional SMS. Some people do this to cut down on data usage. Sometimes there will be a bounce-back text from the carrier that says the number is no longer available or you have been blocked. Have you tried calling yet? I think *67 in front of the number can block it from caller ID. I would try calling and see what happens.