is this woman after my husband?

Jaclyn • Realtor. Wifey. Lucky Lady.
Long before I met my husband(who is a cook) there was a woman and her two daughters, all of them waitresses at my husbands job. They are still to this day very close, which I have no problem with. The mother is so sweet. They all came to our wedding, except the one daughter. Who I think is after my husband. This has been bothering me for a while so I'd apppreciate if you can read and give your thoughts 😬 Before we got married, she was texting him saying she NEEDS to see him BEFORE we get married. Please. They never got together. The next few days after we got married, she sends him a photo from my Facebook page (which were not even friends) and she was asking him if I was pregnant, because I did look like it in that photo. He said no and then she goes, I don't like when people lie to me! Just wanna make sure your happy, something like that... and he says that he is. 
A few months later, she texts him sending him a picture of a mood ring that he bought her and her sister (from the $1 store lol) on her finger 'remember this??' Yeah... when Weill we hang out baby? And then she's saying when her husband is off and she can only han out on tuesdays and Thursday's. my husband texts her back saying he'll let her know. A few days later, I seen those texts and blew up. What is she calling you baby for?! And has to hang out w you only when her husband is off? He said that when they worked together years ago she used to go out to the bar with all of them (him and his other coworkers) after work and her husband is really jealous. Still doesn't explain why they have to hang out when her husband is working. They never hung out anyway.   
So my husbands birthday was last week, she texted him at 11:50pm the night before his bday saying happy birthday! 😘have a great day! Blah blah blah, then she goes, I had a dream about you the other day. Couldn't stop thinking about you. Are you okay? He says yes and she goes okay! Have a great birthday!
Wtf? She always initiates the texts with him. I have suspicions that they had a fling years ago before I came along but he denies it. I just don't understand the way she cares about him so much, and stalking my Facebook page, and sending him flirty text messages... but he says that that's the way they talk to each other.  I know he's not cheating on me, but why is he defending her.. Btw, she doesn't text him often.  These texts  are in a matter of maybe 2 years but she just sent him that birthday text 2 weeks ago.  
Is it even my business if they had something years ago, before I came along? Just asking because I think they did... but he says they didn't..