I would start looking at the coil

 

Go buy a cheap digital multi-meter (every girl should have one). You don't need anything fancy, just a cheap $15 meter will do.

Once you have the meter, turn it on to DC Volts. Remove the seat and start the bike. Put the leads across the battery - red on the positive terminal and black on the negative terminal. See what it's reading. It should be above 13.7 volts. That will tell you if the charging system is working properly.

How old is the battery? It should be changed every 4 to 5 years. The number one thing that kills a battery is vibration.

Report back after testing the charging system.

 

I agree with Big Mike, get a multimeter and start with the easiest thing first.
You don't need a fancy one, a $15 Walmart one can be had in the automotive dept.

Also I have to ask; why do you put the bike on a battery tender daily?
I put mine on a tender only if I don't anticipate riding it for couple of weeks.

If you need to put the bike on the tender everyday, there's either a problem with the battery or charging system.

Lastly, those who mention that you might not be holding the starter down long enough may also be on to something.
Once in a while my 09 Heritage makes the same sound as your's does but it generally only happens once, then the bike starts.

 

The guys talking about the battery are probably on to something....my Heritage was doing something similar when I first bought it (used), put a new battery on it and it hasn't made that noise since.

 

Loose battery cables and worn out batteries can cause a bunch of weird crap to happen, throw in EFI and the problems multiply.

A good tune goes a long way in making your rides enjoyable, HD dealers can't tune the bikes right in my experiences, better off taking it to someone with a dyno, proper tuner and do it right.

 

You shouldn't have the bike on a trickle charger constantly if you're riding it frequently. Like most have said, the battery is probably gonna be the culprit. Let it sit without the trickle charger and see if it will start. Or use the meter to check the battery.

If there was something wrong with the starter I would think the bike would give you problems EVERY TIME you start it.

 

i had an 08 fatboy that was making the same noise when starting warm...searched all around the net for fixes and ended up changing the starter...only had for 2 months after that before i bought my sgs but never had another problem with it

 

I would say your biggest problem is your bike running hot...extreme heat causes the starter solenoid to "heat soak" and draw much more amperage than when cold. (anyone that has ever run headers on a car can attest to this)If your bike doesn't want to start after a gas stop, but starts fine if it cools for 45 minutes....this would be the first thing I would address. A new battery may help a little, but you need to get the bike running cooler...sounds like it is running a tad lean.

 

Excellent point. But I'd still check the voltage first because it is the easiest thing to do. Also, if the battery is 4 years old and hasn't been replaced, she should change it. Why wait until it's completely dead and get stuck some place. Also, a bike 'running hot' has different meanings to different people. If it is as lean as stock, the bike shouldn't be starting hard when 'hot'. But I can hear aftermarket pipes and if she didn't at least get a stage 1 flash, then it's running leaner than stock.

 

Great point about her running too lean. It's hard for us to tell from just reading her post how hot the bike really is running. But if it's as hot as she is saying then that's definitely an issue that needs to be address also. Just a matter of a simple run on a dyno.