Current text was sent with mix of an old text sent to someone else months ago!!

[Eightwings]

I'm concerned!  I sent a text this morning to a friend....it  looked like it was sent as intended on my end. 

When she received the text it was not at all what I had sent!  It was a mix of an of an old text I sent to a business client months ago and a bit of what I had actually sent!

Just to verify,  I copied and pasted what I thought I had sent to her again....and it went through as intended!

Any ideas why a text would combine an old text to a completely different person with a current text?