my student's parents

My friend & I are both tutors. She taught one of my students 2 years. We'll call her *Janice Smith. Anyway, 2 years ago during my friend's birthday Janice & her mom made it a big deal. They brought balloons, flowers, cake & a gift for my friend. I thought it was really sweet. Last year I taught another daughter, we'll call her *Jenna Smith. Last year & this year I've had two Smith girls. On my birthday last year I didn't receive anything (not even a greeting). I didn't think much of it... I just shrugged it off & thought oh, they didn't know. This year the same thing happened. And this time they knew it was my birthday. The funny thing is they give something to my husband on his birthday but not to me. (They know my husband through mutual friends.) I even acknowledge Mrs. Smith's birthday with a greeting & a card with a small gift. 
I've talked to my mil about it & she asked me to think if I've done anything in the past that may have upset Mrs. Smith or her daughters. I thought about it & MAYBE it's because I didn't tell her when I was pregnant when she assumed I was. This was over a year ago now... I needed for her daughter to reschedule a tutoring session due to a doctor's appointment I had & she assumed I was pregnant & asked if I was seeing an OBGYN & I told her I was seeing a family doctor. I didn't want her to know I was pregnant before my husband & I even told our families. 
This is just bizarre to me. What do you all think of it? 
I am a bit hurt by it, but I try not to let it get to me...