My impression is that the OP wants to do short day paddles on her own, for a few hours. A PLB or Spot isn't going to help her significantly, IMO, anymore than a float plan would. If she needs help, she'll need it either immediately (stuck in a strainer, bonked on the head, etc), or within a day (lost boat, stranded above rapids, broken limb, etc). Nothing's going to bring help immediately, and a float plan for a 4 hour trip will bring help an hour or two after your stated return time.
For her type of outings, and her skill level, I think a PLB or Spot might be more of a liability than an aid, as it could simply provide a false sense of security. Also, it could be considered an irresponsible use of rescue resources for someone who is unqualified to go out alone but bring a signalling device, with the idea that even though they lack skills they'll just push a button if they need "saved". (To be clear, I'm not saying this is something that the OP would do. I'm speaking in general terms - suggesting that perhaps novice paddlers should not be encouraged to get electronic signalling devices, when they are concerned that they might not have the skills to do a trip on their own.)
Rescue / Throw Bags
Recreational Kayak Paddle
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