Cocker Spaniel First Season

Question
I have a 15 month old female cocker and I am worried as she hasn't yet had her first season. We would like her to have her first season before she is spayed as apparently it has some longer term health benefits. (Would love to hear your opinion on this!)
Although well behaved she is a very demanding dog compared to our other dog (a Chihuahua). Needing constant interaction, very much like a baby.

Answer
There's a lot of debate about when to spay.  While I do believe in delaying as long as possible, I'm also not convinced about the health benefits of allowing a first heat.  Be aware that you'll have a flock of male dogs trying to get at her and watch her like a hawk.  One of my neighbours subscribed to the first heat theory and while her dog was in her own backyard, a male jumped the fence and bingo - puppies !
15 months is very late and I'd ask your vet's opinion as to why.  Although I can't picture a health issue being the problem.
Yes, cockers can be demanding and you'd better take the alpha role and let her know you "play" when YOU decide to play.  This is aggression..albeit emotional aggression at this point...but it can lead to nipping or worse.  People think cockers are just loveable little fur bundles (and they are) but they're also quite dominant dogs.  Take some action now and don't let this escalate.  The two questions I get here more than any other are skin issues and aggression.  She's demanding because it's been tolerated.
Delores