German Shepherd changing her ways!

[G-Shep Girl]

My Shepherd is an intact 10 year old female. I adopted her at 5 yrs. old, and chose not to have her spayed due to her age and no prior medical history for her. She comes into heat quite often, 2-3 times per year. Two trusted vets have told me that this is not something to be worried about if she seems healthy. She's very healthy, and well adjusted. Really a wonderful dog! Lately, she's been very clingy and vocal, and won't leave me alone. She just came off a heat, and until recently, we were babysitting my sister's Great Dane. Don't know if those two factors, as well as age, are contributing to her clinginess. She's also pretty food motivated, but that doesn't seem to factor in at this point. She keeps pawing me and following me around, and when I sit down with her, she's clingy to the point of distraction. I'm not really concerned about her healthwise, I just think that her age, heat cycle, and the addition of a huge houseguest might contribute to this. The Dane has been gone a few days now, and she's still affectionately over the top!
I love my girl, and I love affection from her, but this is just a new development that is mildy concerning. Hope some of you Shepherd owners can give me some advice, and possibly set my mind at ease.
I've had Shepherds for years, but an unspayed female taht was years old when I adopted her is a new thing for me. Thought I knew my dog, but she's changing and I'd like some help figuring out why! Thanks, everyone!